#include <fstream>
using namespace std;

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

int p, k;

int nr_zero(int n)
{
    int k = 0;
    while (n > 1)
    {
        k = k + n / 5;
        n = n / 5;
    }
    return k;
}

int caut_bin()
{
    int st = 5, dr = p * 5;
    while (st <= dr)
    {
        int mid = (st + dr) / 2;
        int n = nr_zero(mid);
        if (n  >= p)
            dr = mid - 1;
        else
            st = mid + 1;
    }
    return st;
}

void rezolva()
{
    if (p == 0)
        fout << 1;
    else
    {
        int rez = caut_bin();
        fout << rez;
    }
}

int main()
{
    fin >> p;
    rezolva();
    return 0;
}