For a positive integer $ n $, its factorial is defined as the product of all integers from 1 to $ n $, denoted as $ n!$. Now $ n $ double factorial is the product of 1 factorial, 2 factorial, ..., up to $ n $ factorial: $1! \cdot 2! \cdot 3! \cdot \ldots \cdot n!$. Given $ n $, find the number of trailing zeros of a decimal representation of $ n $ double factorial.
Input Format
The first and only line of the standard input contains an integer $ n $ ($1 ≤ n ≤ 10^{18}$).
Output Format
The first and only line of the standard output should contain the number of trailing zeros of $ n $ double factorial.
Example
Input
11
Output
9
Notes
11 double factorial equals 265 790 267 296 391 946 810 949 632 000 000 000. This number has 9 trailing zeros.