#include <fstream>

using namespace std;
ifstream fi("fact.in");
ofstream fo("fact.out");

int p,p2,p5,kk,k5,k;

int main()
{
    //nr tebuie sa aiba p de 2 si p de 5
    fi>>p;
    k=2;
    while(p2<p || p5<p)
    {
        kk=k;
        k5=k;
        while(kk%2==0)
            kk/=2, p2++;
        while(k5%5==0)
            k5/=5, p5++;
        k++;
    }
    k--;
    fo<<k;
    fi.close();
    fo.close();
    return 0;
}