// cum se3calculeaza factorialul unui numar

#include <iostream>
#include <fstream>
using namespace std;
int main()
{ long p,aux,nr;
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
nr=5;
if(p>=100000000)
g<<"-1";
else
    if(p==0)g<<"1";
        else
    {

    while(p>0)
    { aux=nr;
        while (aux%5==0)
            {aux=aux/5;
             p=p-1;
            }
        nr=nr+5;
    }
g<<nr-5;
}


f.close();
g.close();
return 0;
}