cpp没有自带log5，那我就硬搓一个

#include<bits/stdc++.h>
using namespace std;
unsigned long long n;
int main(){
	cin>>n;
	cout<<n/5+n/25+n/125+n/625+n/3125+n/15625+n/78125+n/390625+n/1953125+n/9765625+n/48828125+n/244140625+n/1220703125+n/6103515625+n/30517578125+n/152587890625;
	return 0;
}