#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long x,p,e=25,a;
int main()
{
    f>>p;
    if(p==0)
        g<<1;
        else
        {
            x=p*5;
            while(e<=x)
            {
                x-=((x-1)/e)*5;
                e*=5;
            }
            g<<x;
        }
    return 0;
}