## How To calculate Trailing Zeros in N factorail | count Number of trailing zero in N! CSES problem solution -

This problem is taken form CSES Introductory Problem set. Here You have to count Number of Trailing zero in N!.

## Problem Statement-

Your task is to calculate the number of Trailing Zeros in the factorial .

For example, and it has trailing zeros.

The only input line has an integer .

Print the number of trailing zeros in .

Input:

Output:

For example, and it has trailing zeros.

**Input**The only input line has an integer .

**Output**Print the number of trailing zeros in .

**Constraints****Example**Input:

`20`

Output:

`4`

`Solution-`

Recommended practice yourself Before jumping to solution.

Problem link-https://cses.fi/problemset/task/1618/

So here is A hidden logic behind solving this problem. Think Condition when zero comes as trailing zero when we multiply two numbers.

Zero comes at the end when a number multiplied by 10. So we have to find How many times 10 can be formed in N!.

since 10 is multiple is 2 and 5 so we can get 10 only when 2 and 5 are multiplied so it is better to find how many times we 5 occur in N!.

So For finding number of 5 in N! we have a formula.

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Trailing 0s in n! = Count of 5s in prime factors of n!

= floor(n/5) + floor(n/25) + floor(n/125) + ....

So this is how we can calculate the number of trailing Zeros in N!.

Code Solution of this Problem-