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