#include <fstream>

using namespace std;

long long p,i,u,s,p2,ap,x,m,sum,p5,nr;

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

int main (){

    fin>>p2;

    p = 1;
    u = p2*5;
    while (p<=u){
        m = (p+u)/2;
        p5 = 5;
        nr = 0;
        while (m/p5 > 0){
            nr = m/p5 + nr;
            p5*=5;
        }

        if (nr < p2)
            p = m+1;
        else
            u = m-1;

    }
    p5 = 5;
    nr = 0;
    while (p/p5 > 0){
        nr = p/p5 + nr;
        p5*=5;
    }
    if (nr == p2)
        fout<<p;
    else
        fout<<-1;

    return 0;
}