# Minimum count of numbers required with unit digit X that sums up to N

Given two integers N and X, the task is to find the minimum count of integers with sum N and having unit digit X. If no such representation exists then print -1.
Examples:

Input: N = 38, X = 9
Output:
Explanation:
Minimum two integers are required with unit digit as X to represent as a sum equal to 38.
38 = 19 + 19 or 38 = 29 + 9
Input: N = 6, X = 4
Output: -1
Explanation:
No such representation of

Approach:
Follow the steps below to solve the problem:

• Obtain the unit digit of N and check if it achieved by the sum of numbers whose unit digits are X.
• If it is possible, check if N ? X * ( Minimum number of times a number with unit digit X needs to be added to get sum N).
• If the above condition is satisfied then print the minimum number of times a number with unit digit X needs to be added to get sum N. Otherwise, print -1.

Below is the implementation of the above approach:

 `// C++ Program to implement ` `// the above approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to calculate and return ` `// the minimum number of times a number ` `// with unit digit X needs to be added ` `// to get a sum N ` `int` `check(``int` `unit_digit, ``int` `X) ` `{ ` `    ``int` `times, digit; ` ` `  `    ``// Calculate the number of ` `    ``// additions required to get unit ` `    ``// digit of N ` `    ``for` `(``int` `times = 1; times <= 10; ` `         ``times++) { ` `        ``digit = (X * times) % 10; ` `        ``if` `(digit == unit_digit) ` `            ``return` `times; ` `    ``} ` ` `  `    ``// If unit digit of N ` `    ``// cannot be obtained ` `    ``return` `-1; ` `} ` ` `  `// Function to return the minimum ` `// number required to represent N ` `int` `getNum(``int` `N, ``int` `X) ` `{ ` `    ``int` `unit_digit; ` ` `  `    ``// Stores unit digit of N ` `    ``unit_digit = N % 10; ` ` `  `    ``// Stores minimum addition ` `    ``// of X required to ` `    ``// obtain unit digit of N ` `    ``int` `times = check(unit_digit, X); ` ` `  `    ``// If unit digit of N ` `    ``// cannot be obtained ` `    ``if` `(times == -1) ` `        ``return` `times; ` ` `  `    ``// Otherwise ` `    ``else` `{ ` ` `  `        ``// If N is greater than ` `        ``// or equal to (X*times) ` `        ``if` `(N >= (times * X)) ` ` `  `            ``// Minimum count of numbers ` `            ``// that needed to represent N ` `            ``return` `times; ` ` `  `        ``// Representation not ` `        ``// possible ` `        ``else` `            ``return` `-1; ` `    ``} ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``int` `N = 58, X = 7; ` `    ``cout << getNum(N, X) << endl; ` `    ``return` `0; ` `} `

 `// Java Program to implement ` `// the above approach ` `class` `GFG{ ` `     `  `// Function to calculate and return ` `// the minimum number of times a number ` `// with unit digit X needs to be added ` `// to get a sum N ` `static` `int` `check(``int` `unit_digit, ``int` `X) ` `{ ` `    ``int` `times, digit; ` ` `  `    ``// Calculate the number of ` `    ``// additions required to get unit ` `    ``// digit of N ` `    ``for` `(times = ``1``; times <= ``10``; ` `                    ``times++)  ` `    ``{ ` `        ``digit = (X * times) % ``10``; ` `        ``if` `(digit == unit_digit) ` `            ``return` `times; ` `    ``} ` ` `  `    ``// If unit digit of N ` `    ``// cannot be obtained ` `    ``return` `-``1``; ` `} ` ` `  `// Function to return the minimum ` `// number required to represent N ` `static` `int` `getNum(``int` `N, ``int` `X) ` `{ ` `    ``int` `unit_digit; ` ` `  `    ``// Stores unit digit of N ` `    ``unit_digit = N % ``10``; ` ` `  `    ``// Stores minimum addition ` `    ``// of X required to ` `    ``// obtain unit digit of N ` `    ``int` `times = check(unit_digit, X); ` ` `  `    ``// If unit digit of N ` `    ``// cannot be obtained ` `    ``if` `(times == -``1``) ` `        ``return` `times; ` ` `  `    ``// Otherwise ` `    ``else`  `    ``{ ` ` `  `        ``// If N is greater than ` `        ``// or equal to (X*times) ` `        ``if` `(N >= (times * X)) ` ` `  `            ``// Minimum count of numbers ` `            ``// that needed to represent N ` `            ``return` `times; ` ` `  `        ``// Representation not ` `        ``// possible ` `        ``else` `            ``return` `-``1``; ` `    ``} ` `} ` ` `  `// Driver Code ` `public` `static` `void` `main(String []args) ` `{ ` `    ``int` `N = ``58``, X = ``7``; ` `    ``System.out.println( getNum(N, X)); ` `} ` `} ` ` `  `// This code is contributed by Ritik Bansal `

 `# Python3 program to implement ` `# the above approach ` ` `  `# Function to calculate and return ` `# the minimum number of times a number ` `# with unit digit X needs to be added ` `# to get a sum N ` `def` `check(unit_digit, X): ` `     `  `    ``# Calculate the number of additions ` `    ``# required to get unit digit of N ` `    ``for` `times ``in` `range``(``1``, ``11``): ` `        ``digit ``=` `(X ``*` `times) ``%` `10` `        ``if` `(digit ``=``=` `unit_digit): ` `            ``return` `times ` `             `  `    ``# If unit digit of N ` `    ``# cannot be obtained ` `    ``return` `-``1` ` `  `# Function to return the minimum ` `# number required to represent N ` `def` `getNum(N, X): ` `     `  `    ``# Stores unit digit of N ` `    ``unit_digit ``=` `N ``%` `10` ` `  `    ``# Stores minimum addition ` `    ``# of X required to ` `    ``# obtain unit digit of N ` `    ``times ``=` `check(unit_digit, X) ` ` `  `    ``# If unit digit of N ` `    ``# cannot be obtained ` `    ``if` `(times ``=``=` `-``1``): ` `        ``return` `times ` ` `  `    ``# Otherwise ` `    ``else``: ` ` `  `        ``# If N is greater than ` `        ``# or equal to (X*times) ` `        ``if` `(N >``=` `(times ``*` `X)): ` ` `  `            ``# Minimum count of numbers ` `            ``# that needed to represent N ` `            ``return` `times ` ` `  `        ``# Representation not ` `        ``# possible ` `        ``else``: ` `            ``return` `-``1` ` `  `# Driver Code ` `N ``=` `58` `X ``=` `7` ` `  `print``(getNum(N, X)) ` ` `  `# This code is contributed by Sanjit_Prasad `

 `// C# Program to implement ` `// the above approach ` `using` `System; ` `class` `GFG{ ` `     `  `// Function to calculate and return ` `// the minimum number of times a number ` `// with unit digit X needs to be added ` `// to get a sum N ` `static` `int` `check(``int` `unit_digit, ``int` `X) ` `{ ` `    ``int` `times, digit; ` ` `  `    ``// Calculate the number of ` `    ``// additions required to get unit ` `    ``// digit of N ` `    ``for` `(times = 1; times <= 10; ` `                    ``times++)  ` `    ``{ ` `        ``digit = (X * times) % 10; ` `        ``if` `(digit == unit_digit) ` `            ``return` `times; ` `    ``} ` ` `  `    ``// If unit digit of N ` `    ``// cannot be obtained ` `    ``return` `-1; ` `} ` ` `  `// Function to return the minimum ` `// number required to represent N ` `static` `int` `getNum(``int` `N, ``int` `X) ` `{ ` `    ``int` `unit_digit; ` ` `  `    ``// Stores unit digit of N ` `    ``unit_digit = N % 10; ` ` `  `    ``// Stores minimum addition ` `    ``// of X required to ` `    ``// obtain unit digit of N ` `    ``int` `times = check(unit_digit, X); ` ` `  `    ``// If unit digit of N ` `    ``// cannot be obtained ` `    ``if` `(times == -1) ` `        ``return` `times; ` ` `  `    ``// Otherwise ` `    ``else` `    ``{ ` ` `  `        ``// If N is greater than ` `        ``// or equal to (X*times) ` `        ``if` `(N >= (times * X)) ` ` `  `            ``// Minimum count of numbers ` `            ``// that needed to represent N ` `            ``return` `times; ` ` `  `        ``// Representation not ` `        ``// possible ` `        ``else` `            ``return` `-1; ` `    ``} ` `} ` ` `  `// Driver Code ` `public` `static` `void` `Main() ` `{ ` `    ``int` `N = 58, X = 7; ` `    ``Console.Write(getNum(N, X)); ` `} ` `} ` ` `  `// This code is contributed by Code_Mech `

Output:
```4

```

Time Complexity: O(1)
Auxiliary Space: O(1)

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