#include <fstream>

using namespace std;

ifstream fin("factorial.in");
ofstream gout("factorial.out");

int main()
{
    int n, num = 1, cop;
    fin >> n;
    if (n)
        {num = 0;
        while (n)
        {
            num += 5;
            cop = num;
            while (cop % 5 == 0 && cop)
            {
                cop /= 5;
                n--;
            }
        }
        }
    gout << num;
    return 0;
}