# Given a number x , find y such that x*y + 1 is not a prime

Given a number x, Find y (y > 0) such that x*y + 1 is not a prime.

**Examples:**

Input : 2 Output : 4 Input : 5 Output : 3

Observation:

x*(x-2) + 1 = (x-1)^2 which is not a prime.

Approach :

For x > 2, y will be x-2 otherwise y will be x+2

## C++

`#include <bits/stdc++.h> ` `using` `namespace` `std; ` ` ` `int` `findY(` `int` `x) ` `{ ` ` ` `if` `(x > 2) ` ` ` `return` `x - 2; ` ` ` ` ` `return` `x + 2; ` `} ` ` ` `// Driver code ` `int` `main() ` `{ ` ` ` `int` `x = 5; ` ` ` `cout << findY(x); ` ` ` `return` `0; ` `} ` |

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## Java

`// JAVA implementation of above approach ` ` ` `import` `java.util.*; ` ` ` `class` `GFG ` `{ ` ` ` `public` `static` `int` `findY(` `int` `x) ` ` ` `{ ` ` ` `if` `(x > ` `2` `) ` ` ` `return` `x - ` `2` `; ` ` ` ` ` `return` `x + ` `2` `; ` ` ` `} ` ` ` ` ` `// Driver code ` ` ` `public` `static` `void` `main(String [] args) ` ` ` `{ ` ` ` `int` `x = ` `5` `; ` ` ` `System.out.println(findY(x)); ` ` ` ` ` `} ` ` ` `} ` ` ` ` ` `// This code is contributed ` `// by ihritik ` |

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## Python3

`# Python3 implementation of above ` `# approach ` ` ` `def` `findY(x): ` ` ` ` ` `if` `(x > ` `2` `): ` ` ` `return` `x ` `-` `2` ` ` ` ` `return` `x ` `+` `2` ` ` `# Driver code ` `if` `__name__` `=` `=` `'__main__'` `: ` ` ` `x ` `=` `5` ` ` `print` `(findY(x)) ` ` ` `# This code is contributed ` `# by ihritik ` |

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## C#

`// C# implementation of above approach ` `using` `System; ` ` ` `class` `GFG ` `{ ` `public` `static` `int` `findY(` `int` `x) ` `{ ` ` ` `if` `(x > 2) ` ` ` `return` `x - 2; ` ` ` ` ` `return` `x + 2; ` `} ` ` ` `// Driver code ` `public` `static` `void` `Main() ` `{ ` ` ` `int` `x = 5; ` ` ` `Console.WriteLine(findY(x)); ` `} ` `} ` ` ` `// This code is contributed ` `// by Subhadeep ` |

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## PHP

`<?php ` `// PHP implementation of above approach ` `function` `findY(` `$x` `) ` `{ ` ` ` `if` `(` `$x` `> 2) ` ` ` `return` `$x` `- 2; ` ` ` ` ` `return` `$x` `+ 2; ` `} ` ` ` `// Driver code ` `$x` `= 5; ` `echo` `(findY(` `$x` `)); ` ` ` `// This code is contributed ` `// by Shivi_Aggarwal ` `?> ` |

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**Output :**

3

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