+--------+  +--------+  +-----+
|A1|A2|A3|  |A1|B1|C1|  |A1|B1|
|B1|  |  |  |A2|  |C2|  |A2|C1|
|C1|C2|  |  |A3|  |  |  |A3|C2|
+--------+  +--------+  +-----+