#include <bits/stdc++.h>
using namespace std;

ifstream in ("fact.in");
ofstream out ("fact.out");

long long n, low = 1, high = 500000000;
int rezultat;
int main () {
    //infoarena
    in >> n;
    while (low <= high)
    {
        long long mid = low + (high - low)/2, copie = mid, p=5;
        int nr_zero=0;

        while (mid / p)
        {
            nr_zero += (mid / p);
            p*=5;
        }

        if (nr_zero == n)
        {
            rezultat = copie;
            --high;
        }
        else
        if (nr_zero < n)
            low = mid + 1;
        else
            high = mid - 1;
    }
    out << rezultat;
    in.close();
    out.close();
    return 0;
}