#include <fstream>

using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{
    long long N,y,k,x,p;
    f>>p;
    N=4*p;
    k=0;
    y=5;
    while (N/y>0)
       { k=k+N/y;
         y=y*5;
       }
    if(k<p)
       for(x=N+1;x<=p*5&&k<p;x++)
        {   y=x;
            while(y%5==0)
              {
                  k++;
                  y=y/5;
              }
        }
       if(p==0) g<<1;
           else  if(k==p) g<<x-1;
                     else g<<-1;
       f.close();
       g.close();

    return 0;
}