#include <fstream>
#include <iostream>

using namespace std;

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

long long N, P;
long long nr;

long long zeroes(long long x)
{
    int ans = 0;

    while (x != 0)
    {
        ans += x/5;
        x /= 5;
    }

    return ans;
}

int cautare(int P)
{
    long long ls = 1;
    long long ld = 2000000000;

    long long mid;

    while (ls <= ld)
    {
        mid = (ls + ld) / 2;

        int nr = zeroes(mid);

        if (nr == P)
        {
            return mid - mid%5;
        }

        if (nr >= P)
        {
            ld = mid - 1;
        }
        else
        {
            ls = mid + 1;
        }
    }

    return -1;
}

int main()
{
    f >> P;

    g << cautare(P);

    return 0;
}