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Algebra Level 4

$\begin{cases} {A = 1\times 2 + 3\times4 + 5\times 6 + \ldots+37\times38 + 39 } \\ { B = 1 + 2\times 3 + 4 \times 5 + \ldots + 36 \times 37 + 38 \times 39 } \end{cases}$

The values of $A$ and $B$ are obtained by writing multiplcation and addition operators in an alternating pattern between successive integers as described above. Find $|A-B|$ .

Notation: $| \cdot |$ denotes the absolute value function.