program fact;
var f,h:text;
    p,n,m,c: int64;
begin
  assign(f,'fact.in'); reset(f); readln(f,p); close(f);

  n:=0; c:=0; while c<p do
                begin
                  n:=n+5; m:=n;
                  while m mod 5 =0 do
                     begin
                       m:=m div 5;   inc(c);
                     end
                end;
   if c<>p then n:=-1;

  assign(h,'fact.out'); rewrite(h); writeln(h,n);
  close(h);
end.