//
// Created by dragos on 28.01.2019.
//

#include <iostream>
#include <fstream>

using namespace std;

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

int p;
int main() {

    fin>>p;

    if(p == 0) {
        fout<<1;
    } else {
        double k = p;
        for(; k > 1; k /= 5.0);

        if(k == 1.0) {
            fout<< -1;
        } else if(p < 5) {
            fout<< (p - p / 5) * 5;
        } else {
            fout<< (p - p / 5 + 1) * 5;
        }
    }

    fin.close();
    fout.close();

    return 0;
}