#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long p,s,i,j,r,k;
int main()
{
   fin>>p;
   j=p-p/5-1;
   s=0;
   k=0;
   while (s!=p&&j<p&&k<100000)
     {
       k++;
       j++;
       s=0;
       i=j;
       while (i>0)
         {
           s+=i;
           i/=5;
         }
     }
   if (p==0)
     fout<<1;
    else
     if (s==p)
       fout<<j*5;
      else
        fout<<-1;
   return 0;
}