#include <fstream>

inline long long nr0(long long n) {
    long long s = 0, c = 5;
    while (c < n) {
        s += n / c;
        c *= 5;
    }
    return s;
}

int main() {
    std::ifstream in("fact.in");
    std::ofstream out("fact.out");
    long long p, r = 0, pas = 1 << 30;
    in >> p;
    p--;
    while (pas > 0) {
        if (nr0(r + pas) <= p) r += pas;
        pas >>= 1;
    }
    r++;
    if (nr0(r) == p + 1) out << r;
    else out << -1;
    return 0;
}