#include <fstream>
using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int p,i,j,dev;

int zero(int poz)
{
    int suma = 0;
    while(poz)
    {
        suma += poz / 5;
        poz /= 5;
    }
    return suma;
}

int main ()
{

    in>>p;
    dev = 1 << 30;
    while(dev)
    {
        if(zero(i+dev) < p)
            i+=dev;
        dev/=2;
    }
    i += 1;
    if(zero(i) == p)
        out << i << "\n";
    else
        out << "-1\n";
    return 0;
}