# Print the kth common factor of two numbers

• Difficulty Level : Basic
• Last Updated : 22 Jun, 2022

Given three numbers x, y and k, find the k’th common factor of x and y. Print -1 if there are less than k common factors of x and y.
Examples :

```Input : x = 20, y = 24
k = 3
Output : 4
Common factors are 1, 2, 4, ...

Input : x = 4, y = 24
k = 2
Output : 2

Input : x = 22, y = 2
k = 3
Output : -1```

We find the smaller of two numbers as common factor cannot be greater than the smaller number. Then we run a loop from 1 to the smaller number. For every number i, we check if it is a common factor. If yes, we increment count of common factors.
Below is the Implementation :

## C++

 `// C++ program to find kth common factor``// of two numbers``#include``using` `namespace` `std;` `// Returns k'th common factor of x and y.``int` `findKCF(``int` `x, ``int` `y, ``int` `k)``{``   ``// Find smaller of two numbers``   ``int` `small = min(x, y);` `   ``// Count common factors until we either``   ``// reach small or count becomes k.``   ``int` `count = 1;``   ``for` `(``int` `i=2; i<=small; i++)``   ``{``      ``if` `(x % i==0 && y % i == 0)``         ``count++;``      ``if` `(count == k)``         ``return` `i;``   ``}` `   ``// If we reached small``   ``return` `-1;``}` `// Driver code``int` `main()``{``   ``int` `x = 4, y = 24, k = 3;``   ``cout << findKHCF(x, y, k);``   ``return` `0;``}`

## Java

 `// Java program to find kth``// common factor of two numbers``import` `java.lang.*;` `class` `GFG {``    ` `// Returns k'th common factor of x and y.``static` `int` `findKHCF(``int` `x, ``int` `y, ``int` `k) {``    ` `    ``// Find smaller of two numbers``    ``int` `small = Math.min(x, y);` `    ``// Count common factors until we either``    ``// reach small or count becomes k.``    ``int` `count = ``1``;``    ``for` `(``int` `i = ``2``; i <= small; i++) {``    ``if` `(x % i == ``0` `&& y % i == ``0``)``        ``count++;``    ``if` `(count == k)``        ``return` `i;``    ``}` `    ``// If we reached small``    ``return` `-``1``;``}` `// Driver code``public` `static` `void` `main(String[] args) {``    ` `    ``int` `x = ``4``, y = ``24``, k = ``3``;``    ``System.out.print(findKHCF(x, y, k));``}``}` `// This code is contributed by Anant Agarwal.`

## Python3

 `# Python program to find``# kth common factor``# of two numbers` `# Returns k'th common``# factor of x and y.``def` `findKHCF(x,y,k):` `    ``# Find smaller of two numbers``    ``small ``=` `min``(x, y)`` ` `    ``# Count common factors``    ``# until we either``    ``# reach small or count``    ``# becomes k.``    ``count ``=` `1``    ``for` `i ``in` `range``(``2``,small``+``1``):``   ` `        ``if` `(x ``%` `i``=``=``0` `and` `y ``%` `i ``=``=` `0``):``            ``count``=``count ``+` `1``        ``if` `(count ``=``=` `k):``            ``return` `i``   ` ` ` `    ``# If we reached small``    ``return` `-``1` `# Driver code` `x ``=` `4``y ``=` `24``k ``=` `3``print``(findKHCF(x, y, k))` `# This code is contributed``# by Anant Agarwal.`

## C#

 `// C# program to find kth``// common factor of two numbers``using` `System;` `class` `GFG {``    ` `// Returns k'th common factor of x and y.``static` `int` `findKHCF(``int` `x, ``int` `y, ``int` `k)``{``    ` `    ``// Find smaller of two numbers``    ``int` `small = Math.Min(x, y);` `    ``// Count common factors until we either``    ``// reach small or count becomes k.``    ``int` `count = 1;``    ``for` `(``int` `i = 2; i <= small; i++)``    ``{``        ``if` `(x % i == 0 && y % i == 0)``            ``count++;``        ``if` `(count == k)``            ``return` `i;``    ``}` `    ``// If we reached small``    ``return` `-1;``}` `// Driver code``public` `static` `void` `Main()``{``    ``int` `x = 4, y = 24, k = 3;``    ``Console.Write(findKHCF(x, y, k));``}``}` `// This code is contributed by Nitin Mittal.`

## PHP

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## Javascript

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Output :

`4`

Time complexity: O(n) where n is smallest among (x,y)

Auxiliary space: O(1)

This article is contributed by Afzal Ansari. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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