#include <iostream>
#include <fstream>

using namespace std;

int P;
int N = 0;
int trailingZeros = 0;

void solve() {
    while (trailingZeros < P) {
        int aux;

        if (trailingZeros + 6 < P) {
            N += 25;
            trailingZeros += 6;
            aux = N / 25;
        }
        else {
            N += 5;
            aux = N;
        }

        while (aux % 5 == 0) {
            aux /= 5;
            trailingZeros++;
        }
    }

    cout << N;
}

int main() {
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);

    cin >> P;
    if (P == 0) {
        cout << 1;
        return 0;
    }

    solve();
}