#include <fstream>

int main() {
    std::ifstream in("fact.in");
    std::ofstream out("fact.out");
    long long p, r = 0, pas = 1 << 30, n, s, c;
    in >> p;
    p--;
    while (pas > 0) {
        n = r + pas;
        s = 0;
        c = 5;
        while (c < n) {
            s += n / c;
            c *= 5;
        }
        if (s <= p) r += pas;
        pas >>= 1;
    }
    out << ++r;
    return 0;
}