#include <fstream>
#include <cmath>
#define nmax 400000020
using namespace std;
ifstream f("factorial.in");
ofstream g("factorial.out");
int numar, P;

int main()
{int Aux, x = 0;
    f >> P;
    if(P == 0) g<<1<<'\n';
    else{
        Aux = P;
        numar = 25;
        P *= 5;

        while (numar <= P){
            P -= ((P - 1) / numar) * 5;
            numar *= 5;
        }
        numar /= 5;
        while(numar >= 5){
            x += P / numar;
            numar /= 5;
        }

        if(x == Aux) g << P << '\n';
            else g << -1 <<'\n';
    }
    return 0;
}