Problem Link: LightOJ 1138

We can easily calculate trailing zeros in n!. But, this problem refers to find the smallest n where n! holds exactly k trailing zeros.

If you don’t know how to calculate trailing zeros of n!. Read here – Trailing Zeros.

The max range is 10^8. So, 5*10^8! can hold this amount of trailing zero ( using only 5^1 factors ). As, the number of trailing zero increases with the increment of n. Now, search for n and check if that contains k trailing zero or not. Factorial of multiple numbers can contain same numbers of trailing zero, in this problem you just have to find the smallest one, which is obviously a multiple of 5. Now, code it and have a green verdict…

## Code:

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— H. L. Menckeneverycomplexproblemthere is an answer that is clear, simple, andwrong“