#include <fstream>

using namespace std;

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

int nrZero(long long n)
{
    int ex = 0, pp = 5;
    while(n >= pp)
    {
        ex += n / pp;
        pp *= 5;
    }
    return ex;
}

long long cautbin(int p)
{
    long long st = 1, dr = 1000000000, mij, poz = -1;
    int nz;
    while (st <= dr)
    {
        mij = st + (dr - st) / 2;
        nz = nrZero(mij);
        if (nz == p)
        {
            poz = mij;
            dr = mij - 1;
        }
        else
        {
            if (nz > p)
                dr = mij - 1;
            else
                st = mij + 1;
        }
    }
    return poz;
}

int main()
{
    int p;
    in >> p;
    out << cautbin(p);
    return 0;
}