# Grids & Bubbles

Logic Level 2

The above is a $3\times 3$ table, where each cell consists of a distinct digit from 1 to 9 with 7 in the center.

The circular bubbles on the borderlines indicate the absolute differences between the pair of numbers in the neighboring cells, 8 of which are known and colored yellow, and 4 of which--A, B, C, D--are unknown and colored red.

What is the 4-digit integer $\overline{ABCD}?$

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