#include <fstream>

using namespace std;

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

int main ()
{
    int p,c,gasit;
    long long s,d,m,x;
    s=1;
    d=1000000000;
    fin>>p ;
    gasit=0;
    while(s<=d && gasit==0)
        {
         m=(s+d)/2;
         x=m;
         c=0;
         while(x!=0)
            {
             c=c+x/5 ;
             x=x/5;
            }
         if(c==p)
            {
             if(p==0) fout<<"1";
                else fout<<m-m%5;
             gasit=1;
            }
         else if (c>p) d=m-1;
            else s=m+1;
        }
    if(gasit==0) fout<<"-1";
    fin.close();
    fout.close();
    return 0;
 }