#include <fstream>

using namespace std;

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

int n,p,u,m;

int putere(int v) {
    int x=0,c=5;
    while (v>=c) {
        x+=v/c;
        c*=5;
    }
    return x;
}

int main () {
    f >> n;
    p=1;u=5*n;
    while (p<=u) {
        m=(p+u)/2;
        if (putere(m)<n) p=m+1;
                    else u=m-1;
    }
    if (putere(p)==n) g << p << '\n';
                 else g << -1 << '\n';
    f.close();g.close();
    return 0;
}