#include <fstream>

using namespace std;

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

int p;

int nrzero(int nr) {
    int s = 0;
    while (nr >= 5) {
        s += nr / 5;
        nr /= 5;
    }
    return s;
}

int cautbin() {
    int r = 0, pas = 1 << 29;
    while (pas != 0) {
        if (nrzero(r + pas) < p) {
            r += pas;
        }
        pas >>= 1;
    }
    if (nrzero(r + 1) == p) return r + 1;
    else return -1;
}

int main()
{
    in >> p;
    out << cautbin();
}