uses
  GraphABC;

var
  x1, y1, x2, y2: integer;

begin
  y1:=0;
  y2:= 400;
  while x1 <> 640 do
  begin
    x1 := x1 + 10;
    x2 := x2 + 10;
    line(x1, y1, x2, y2);
  end;
  x1:=0;
  x2:=640;
  y1:=0;
  y2:=0;
  while y1<>400 do
  begin
  y1:=y1+10;
  y2:=y2+10;
  line(x1, y1, x2, y2);
  end;
  x1:=0;
  x2:=0;
  y1:=0;
  y2:=0;
  while (x1<>640)  and (y2<>400) do
  begin
  x1:=x1+10;
  y2:=y2+10;
  line(x1, y1, x2, y2);
  end;
  while (x1<>640)  and (y2<>400) do
  begin
  x1:=x1+10;
  y2:=y2+10;
  line(x1, y1, x2, y2);
  end;
  while x1<>640 do
  begin
  x1:=x1+10;
  x2:=x2+10;
  line(x1, y1, x2, y2);
  end;
  while (x2<>640)  and (y1<>400) do
  begin
  x2:=x2+10;
  y1:=y1+10;
  line(x1, y1, x2, y2);
  end;
  x1:=640;
  x2:=640;
  y1:=0;
  y2:=0;
  while (x1<>0)  and (y1<>400) do
  begin
  x1:=x1+10;
  y1:=y1+10;
  line(x1, y1, x2, y2);
  end;
  x1 := 640;
  x2 := 640;
  y1 := 0;
  y2 := 0;
  while (x1 <> 0)  and (y2 <> 400) do
  begin
    x1 := x1 - 10;
    y2 := y2 + 10;
    line(x1, y1, x2, y2);
  end;
  while x1<>0 do
  begin
  x1:=x1-10;
  x2:=x2-10;
  line(x1, y1, x2, y2);
  end;
  while y1<>400 do
  begin
  y1:=y1+10;
  x2:=x2-10;
  line(x1, y1, x2, y2);
  end;
end.