#include <iostream>
#include <fstream>

using namespace std;

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

int main() {

    long a;
    in >> a;

    if(a == 0) {
        out << 1;
        return 0;
    }
    /*if((a+1)%6 == 0) {
        out << "-1";
        return 0;
    }

    long dec = (a+1)/6;

    out << a*5 - dec*5;*/

    long long nr = 0;
    long long sec = 0;
    //long fact2 = 0;
    long fact5 = 0;

    while(true) {

        nr++;
        sec = nr;

        /*while(sec%2 == 0 && sec != 0) {
            fact2++;
            sec /= 2;
        }*/
        //sec = nr;
        while(sec%5 == 0 && sec != 0) {
            fact5++;
            sec /= 5;
        }

        if(fact5 == a) {
            out << nr;
            break;
        } else if(fact5 > a) {
            out << "-1";
            break;
        }

    }

    return 0;
}