#include <iostream>
#include <fstream>
using namespace std;
int main()
{
    unsigned long long p,i,j;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    for(i=1;i<=p;i++)
    {
        j=i;
        while(j%5==0)
        {
            p--;
            j=j/5;
        }

    }
    p=p*5;

    if(p)
        g<<p;
    else
        g<<"1";

    return 0;
}