$x_1{y}_1$

$x_1=y_1\Rightarrow \overline{x_1\oplus y_1}$

$x_1>y_1\Rightarrow x_1\overline{y_1}$

$x_1<y_1\Rightarrow \overline{x_1}{y}_1$

00

1

0

0

01

0

0

1

10

0

1

0

11

1

0

0