var x:int,y:int;

begin
  x = 0; 
  y = 0;
  while (x<=99) do
    if x<=49 then 
      x = x+1;
      y = y+1; 
    else 
      x = x+1;
      y = y-1;
    endif;
  done;
  if (y < 0) then fail; endif;
end