# include<fstream>
using namespace std;

int nr_zerouri(int d)
{
    int n;
    n=0;
    while (d>4)
    {
        d=d/5;
        n=n+d;
    }
    return n;
}

int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    int p,n,a,b,d;
    fin >> p;

    if (p==0)
    {
        fout<<1;
    }
    else
    {
        a=1;
        b=2000000000;
        while(a<=b)
        {
            d=(a+b)/2;
            n=nr_zerouri(d);
            if(n<p)
            {
                a=d+1;
            }
            else
            {
                b=d-1;
            }
        }
        n=nr_zerouri(a);
        if(n!=p)
        {
          fout << -1 ;
        }
        else
        {
            fout<<a;
        }
   }
   fout.close();
   return 0;
}