#include<iostream>
using namespace std;
int dan(unsigned long long int n)
{
    unsigned long long int i=0;
    while(n>=5)
    {
        n=n/5;
        i=i+n;
    }
    return i;
}
int jiecheng(unsigned long long int n)
{
	unsigned long long int i,j=0;
	for(i=1;i<=n;i++)
	{
		j=j+dan(i);
	}
	return j;
}
int main()
{
    unsigned long long int y;
    cin>>y;
    cout<<jiecheng(y);
    return 0;
}

第一个点为什么WA