The expressions $A$ = $1\times 2 + 3\times 4 + 5\times 6 + \cdots + 37 \times 38 + 39$ and $B$ = $1 + 2 \times 3 + 4\times 5 + \cdots + 36\times 37 + 38\times 39$ are obtained by writing multiplication and addition operators in an alternating pattern between successive integers. Find the positive difference between integers $A$ and $B$.