program Factorial;
var p,n,m:int64;
r:real;
f,iesire:text;
begin
   assign(f,'fact.in');
 assign(iesire,'fact.out');
 Reset(f);
 rewrite(iesire);
  readln(f,p);
  if(p=0) then n:=1 else
    if(p<0) then n:=-1 else
  n := 5*p;
  if(n>=25) then begin
    r:=n;
    while r>=25 do
    begin  
      r := r/25;
      inc(m);
    end;
    n := n-(n div 25 -1)*5*m;
    end;
  writeln(iesire,n);
  close(iesire);
end.