{Se da un numar intreg P.
Sa se gaseasca cel mai mic numar natural strict pozitiv N pentru care
N! are exact P cifre de 0 la sfarsit.
Se stie ca N! = 1 * 2 * 3 * .... * (N - 1) * N.
}
program factorial;
var f:textfile;
    p, fact:longint;
begin
   assign(f, 'fact.in');
   reset(f);
   read(f, p);
   close(f);
   //readln(p);
   if p<5 then fact:=p*5
      else if p>5 then fact:=p*5-5
      else fact:=-1;

   assign(f, 'fact.out');
   rewrite(f);
   write(f, fact);
   close(f);
   {writeln(fact);
   readln }
end.