#include <iostream.h>
#include <fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
long p,s,k;
int i;
long sk()
{long sum=0, d=5;
   while(d<=k) {sum+=k/d; d*=5;}
 return sum;
}


int main(void)
{f>>p;
 k=p/6;
 if(k==0)
      if(p==5) g<<-1<<'\n'; else if(p==0) g<<1<<'\n'; else g<<p*5<<'\n';
  else
   {s=sk();
    while(6*k+4+s>=p)
     {k--;
      s=sk();
     }
    k++; s=sk();
    if(p<6*k+s) g<<-1<<'\n';
     else g<<(p-s-k)*5<<'\n';
   }
 g.close(); f.close(); return 0;
}