#include <fstream>
using namespace std;
int n,a,zero,aux, p;
int main () {
    ifstream fin ("fact.in");
    ofstream fout ("fact.out");
    fin>>n;

    for (a = 1; ;a++) {
        /// calculez cate zerouri are in coara a!

        p = 5;
        zero = 0;
        while (p <= a) {
            zero += a / p;
            p *= 5;
        }
        if (zero == n) {
            fout<<a;
            break;
        }
        if (zero > n) {
            fout<<-1;
            break;
        }

    }
    return 0;
}