#include <iostream>
#include <chrono>
#include <fstream>

using namespace std::chrono;

std::ifstream f1("fact.in");
std::ofstream f2("fact.out");


//int pof(int t) {
//    if (t % 5 == 0) {
//        return 1 + pof(t / 5);
//    }
//    return 1;
//}

int zeros(int n) {
    int res = 0;
    while (n = n / 5) {
        res += n;
    }
    return res;
}

void factorial() {
    int target;
//    std::ifstream f1("../in.txt");
//    std::ofstream f2("../out.txt");

    f1 >> target;

    for (int i = 0;; i += 5) {
        int zr = zeros(i);
        if (zr == target) {
            f2 << i << std::endl;
            return;
        }
    }

//    int counter = 0;
//    while (target > 0) {
//        counter += 5;
//        target -= pof(counter / 5);
//    }
//    f2 << counter << std::endl;
}

int main() {
    auto start = high_resolution_clock::now();

    factorial();

    auto stop = high_resolution_clock::now();
    auto duration = duration_cast<milliseconds>(stop - start);
    std::cout << std::endl << "[time]:" << duration.count() << std::endl;
    return 0;
}