Math
Count the number of zeros at the end of n! (n factorial). n! itself is far too large to compute, so work out the answer from the factors of n!.
Input
A single integer n.
Output
Print the number of trailing zeros of n!.
Constraints
0 <= n <= 10^9
Example 1
Input
5
Output
1
5! = 120 has one trailing zero.
Example 2
Input
25
Output
6
Five multiples of 5 plus one extra from 25 itself.