# Find the Nth element of the modified Fibonacci series

Given two integers A and B which are the first two terms of the series and another integer N. The task is to find the Nth number using Fibonacci rule i.e. fib(i) = fib(i – 1) + fib(i – 2)

Example:

Input: A = 2, B = 3, N = 4
Output: 8
The series will be 2, 3, 5, 8, 13, 21, …
And the 4th element is 8.

Input: A = 5, B = 7, N = 10
Output: 343

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Intilalize variable sum = 0 that stores sum of the previous two values. Now, run a loop from i = 2 to N and for each index update value of sum = A + B and A = B, B = sum. Then, finally return the sum which is the required Nth element.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to return the Nth number of ` `// the modified Fibonacci series where ` `// A and B are the first two terms ` `int` `findNthNumber(``int` `A, ``int` `B, ``int` `N) ` `{ ` ` `  `    ``// To store the current element which ` `    ``// is the sum of previous two ` `    ``// elements of the series ` `    ``int` `sum = 0; ` ` `  `    ``// This loop will terminate when ` `    ``// the Nth element is found ` `    ``for` `(``int` `i = 2; i < N; i++) { ` `        ``sum = A + B; ` ` `  `        ``A = B; ` ` `  `        ``B = sum; ` `    ``} ` ` `  `    ``// Return the Nth element ` `    ``return` `sum; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `A = 5, B = 7, N = 10; ` ` `  `    ``cout << findNthNumber(A, B, N); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach ` `import` `java.util.*; ` ` `  `class` `GFG  ` `{ ` ` `  `    ``// Function to return the Nth number of ` `    ``// the modified Fibonacci series where ` `    ``// A and B are the first two terms ` `    ``static` `int` `findNthNumber(``int` `A, ``int` `B, ``int` `N)  ` `    ``{ ` ` `  `        ``// To store the current element which ` `        ``// is the sum of previous two ` `        ``// elements of the series ` `        ``int` `sum = ``0``; ` ` `  `        ``// This loop will terminate when ` `        ``// the Nth element is found ` `        ``for` `(``int` `i = ``2``; i < N; i++) ` `        ``{ ` `            ``sum = A + B; ` ` `  `            ``A = B; ` ` `  `            ``B = sum; ` `        ``} ` ` `  `        ``// Return the Nth element ` `        ``return` `sum; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``int` `A = ``5``, B = ``7``, N = ``10``; ` ` `  `        ``System.out.println(findNthNumber(A, B, N)); ` `    ``} ` `}  ` ` `  `// This code is contributed by PrinciRaj1992 `

## Python3

 `# Python3 implementation of the approach ` ` `  `# Function to return the Nth number of ` `# the modified Fibonacci series where ` `# A and B are the first two terms ` `def` `findNthNumber(A, B, N): ` ` `  `    ``# To store the current element which ` `    ``# is the sum of previous two ` `    ``# elements of the series ` `    ``sum` `=` `0` ` `  `    ``# This loop will terminate when ` `    ``# the Nth element is found ` `    ``for` `i ``in` `range``(``2``, N): ` `        ``sum` `=` `A ``+` `B ` ` `  `        ``A ``=` `B ` ` `  `        ``B ``=` `sum` `     `  `    ``# Return the Nth element ` `    ``return` `sum` ` `  `# Driver code ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``A ``=` `5` `    ``B ``=` `7` `    ``N ``=` `10` ` `  `    ``print``(findNthNumber(A, B, N)) ` ` `  `# This code is contributed by Ashutosh450 `

## C#

 `// C# implementation of the approach ` `using` `System; ` ` `  `class` `GFG  ` `{ ` ` `  `    ``// Function to return the Nth number of ` `    ``// the modified Fibonacci series where ` `    ``// A and B are the first two terms ` `    ``static` `int` `findNthNumber(``int` `A, ``int` `B, ``int` `N)  ` `    ``{ ` ` `  `        ``// To store the current element which ` `        ``// is the sum of previous two ` `        ``// elements of the series ` `        ``int` `sum = 0; ` ` `  `        ``// This loop will terminate when ` `        ``// the Nth element is found ` `        ``for` `(``int` `i = 2; i < N; i++) ` `        ``{ ` `            ``sum = A + B; ` ` `  `            ``A = B; ` ` `  `            ``B = sum; ` `        ``} ` ` `  `        ``// Return the Nth element ` `        ``return` `sum; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``int` `A = 5, B = 7, N = 10; ` ` `  `        ``Console.WriteLine(findNthNumber(A, B, N)); ` `    ``} ` `} ` ` `  `// This code is contributed by AnkitRai01 `

Output:

```343
```

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