var n,now,time:longint;
begin
 readln(n);
 now:=1;
 time:=0;
 while true do begin
  n:=n-now;
  if n-(now+1)<0 then now:=1
  else inc(now);
  inc(time);
  if n<=0 then break;
 end;
 writeln(time);
close(input);
close(output);
end.