Given two numbers **A** and **B**. The task is to find the smallest positive integer greater than or equal to 1 such that the sum of all three numbers become a prime number.

**Examples:**

Input:A = 2, B = 3

Output:2

Explaination:

The third number is 2 because if we add all three number the

sum obtained is 7 which is a prime number.

Input:A = 5, B = 3

Output:3

**Approach: **

- First of all store the sum of given 2 number in
**sum**variable. - Now, check if
**bitwise and (&)**of sum and 1 is equal to 1 or not (checking if the number is odd or not). - If it is equal to 1 then assign 2 to variable
**temp**and go to step 4. - Else check sum value of sum and temp variable whether it is prime number or not. If prime, then print the value of temp variable else add 2 to temp variable untill it is less than a prime value.

Below is the implementation of the above approach:

## C++

`// C++ implementation of the above approach ` `#include <bits/stdc++.h> ` `using` `namespace` `std; ` ` ` `// Function that will check ` `// whether number is prime or not ` `bool` `prime(` `int` `n) ` `{ ` ` ` `for` `(` `int` `i = 2; i * i <= n; i++) { ` ` ` ` ` `if` `(n % i == 0) ` ` ` `return` `false` `; ` ` ` `} ` ` ` `return` `true` `; ` `} ` ` ` `// Function to print the 3rd number ` `void` `thirdNumber(` `int` `a, ` `int` `b) ` `{ ` ` ` `int` `sum = 0, temp = 0; ` ` ` ` ` `sum = a + b; ` ` ` `temp = 1; ` ` ` ` ` `// If the sum is odd ` ` ` `if` `(sum & 1) { ` ` ` `temp = 2; ` ` ` `} ` ` ` ` ` `// If sum is not prime ` ` ` `while` `(!prime(sum + temp)) { ` ` ` `temp += 2; ` ` ` `} ` ` ` ` ` `cout << temp; ` `} ` ` ` `// Driver code ` `int` `main() ` `{ ` ` ` `int` `a = 3, b = 5; ` ` ` ` ` `thirdNumber(a, b); ` ` ` ` ` `return` `0; ` `} ` |

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## Java

`// Java implementation of the approach ` `import` `java.util.*; ` ` ` `class` `GFG ` `{ ` ` ` `// Function that will check ` `// whether number is prime or not ` `static` `boolean` `prime(` `int` `n) ` `{ ` ` ` `for` `(` `int` `i = ` `2` `; i * i <= n; i++) ` ` ` `{ ` ` ` `if` `(n % i == ` `0` `) ` ` ` `return` `false` `; ` ` ` `} ` ` ` `return` `true` `; ` `} ` ` ` `// Function to print the 3rd number ` `static` `void` `thirdNumber(` `int` `a, ` `int` `b) ` `{ ` ` ` `int` `sum = ` `0` `, temp = ` `0` `; ` ` ` ` ` `sum = a + b; ` ` ` `temp = ` `1` `; ` ` ` ` ` `// If the sum is odd ` ` ` `if` `(sum == ` `0` `) ` ` ` `{ ` ` ` `temp = ` `2` `; ` ` ` `} ` ` ` ` ` `// If sum is not prime ` ` ` `while` `(!prime(sum + temp)) ` ` ` `{ ` ` ` `temp += ` `2` `; ` ` ` `} ` ` ` `System.out.print(temp); ` `} ` ` ` `// Driver code ` `static` `public` `void` `main (String []arr) ` `{ ` ` ` `int` `a = ` `3` `, b = ` `5` `; ` ` ` ` ` `thirdNumber(a, b); ` `} ` `} ` ` ` `// This code is contributed by 29AjayKumar ` |

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## Python3

`# Python3 implementation of the above approach ` ` ` `# Function that will check ` `# whether number is prime or not ` `def` `prime(n): ` ` ` `for` `i ` `in` `range` `(` `2` `, n ` `+` `1` `): ` ` ` `if` `i ` `*` `i > n ` `+` `1` `: ` ` ` `break` ` ` ` ` `if` `(n ` `%` `i ` `=` `=` `0` `): ` ` ` `return` `False` ` ` ` ` `return` `True` ` ` `# Function to print the 3rd number ` `def` `thirdNumber(a, b): ` ` ` `summ ` `=` `0` ` ` `temp ` `=` `0` ` ` ` ` `summ ` `=` `a ` `+` `b ` ` ` `temp ` `=` `1` ` ` ` ` `#If the summ is odd ` ` ` `if` `(summ & ` `1` `): ` ` ` `temp ` `=` `2` ` ` ` ` `#If summ is not prime ` ` ` `while` `(prime(summ ` `+` `temp) ` `=` `=` `False` `): ` ` ` `temp ` `+` `=` `2` ` ` ` ` `print` `(temp) ` ` ` `# Driver code ` `a ` `=` `3` `b ` `=` `5` ` ` `thirdNumber(a, b) ` ` ` `# This code is contributed by Mohit Kumar ` |

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## C#

`// C# implementation of the above approach ` `using` `System; ` ` ` `class` `GFG ` `{ ` ` ` `// Function that will check ` `// whether number is prime or not ` `static` `bool` `prime(` `int` `n) ` `{ ` ` ` `for` `(` `int` `i = 2; i * i <= n; i++) ` ` ` `{ ` ` ` `if` `(n % i == 0) ` ` ` `return` `false` `; ` ` ` `} ` ` ` `return` `true` `; ` `} ` ` ` `// Function to print the 3rd number ` `static` `void` `thirdNumber(` `int` `a, ` `int` `b) ` `{ ` ` ` `int` `sum = 0, temp = 0; ` ` ` ` ` `sum = a + b; ` ` ` `temp = 1; ` ` ` ` ` `// If the sum is odd ` ` ` `if` `(sum == 0) ` ` ` `{ ` ` ` `temp = 2; ` ` ` `} ` ` ` ` ` `// If sum is not prime ` ` ` `while` `(!prime(sum + temp)) ` ` ` `{ ` ` ` `temp += 2; ` ` ` `} ` ` ` `Console.Write (temp); ` `} ` ` ` `// Driver code ` `static` `public` `void` `Main () ` `{ ` ` ` `int` `a = 3, b = 5; ` ` ` ` ` `thirdNumber(a, b); ` `} ` `} ` ` ` `// This code is contributed by Sachin. ` |

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**Output:**

3

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