for i := 2 to 4 do
    for j := 4 downto i do
      if (x1[j] < x1[j - 1]) then begin

        c := x1[j];
        x1[j - 1] := x1[j];
        x1[j] := c;

        c := x2[j];
        x2[j - 1] := x2[j];
        x2[j] := c;

      end;

  for i := 2 to 4 do
    for j := 4 downto i do
      if (y1[j] < y1[j - 1]) then begin

        c := y1[j];
        y1[j - 1] := y1[j];
        y1[j] := c;

        c := y2[j];
        y2[j - 1] := y2[j];
        y2[j] := c;

      end;