#include <fstream>
#include <cmath>
#include <iostream>

int main()
{
    std::ifstream f("fact.in");
    std::ofstream g("fact.out");

    int zeroes;
    f >> zeroes;
    if (!zeroes) {
        g << 1 << "\n";
        return 0;
    }
    int i = 0, j = 1;
    double l5 = log(5);
    while (i < zeroes) {
        if (j % 5)
            i += 1;
        else
            i += (int)(log(j * 5) / l5);
        j++;
    }

    g << (j - 1) * 5 << "\n";
}