# C# Program to Count trailing zeroes in factorial of a number

Given an integer n, write a function that returns count of trailing zeroes in n!.

**Examples :**

Input: n = 5 Output: 1 Factorial of 5 is 120 which has one trailing 0. Input: n = 20 Output: 4 Factorial of 20 is 2432902008176640000 which has 4 trailing zeroes. Input: n = 100 Output: 24

Trailing 0s in n! = Count of 5s in prime factors of n! = floor(n/5) + floor(n/25) + floor(n/125) + ....

## C#

`// C# program to count` `// trailing 0s in n!` `using` `System;` ` ` `class` `GFG {` ` ` ` ` `// Function to return trailing` ` ` `// 0s in factorial of n` ` ` `static` `int` `findTrailingZeros(` `int` `n)` ` ` `{` ` ` `// Initialize result` ` ` `int` `count = 0;` ` ` ` ` `// Keep dividing n by powers` ` ` `// of 5 and update count` ` ` `for` `(` `int` `i = 5; n / i >= 1; i *= 5)` ` ` `count += n / i;` ` ` ` ` `return` `count;` ` ` `}` ` ` ` ` `// Driver Code` ` ` `public` `static` `void` `Main()` ` ` `{` ` ` `int` `n = 100;` ` ` `Console.WriteLine(` `"Count of trailing 0s in "` ` ` `+ n + ` `"! is "` `+ findTrailingZeros(n));` ` ` `}` `}` ` ` `// This code is contributed by vt_m` |

**Output:**

Count of trailing 0s in 100! is 24

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