Each row and column has exactly one A, one B, one C, and one D. In the following square, the outside letters show which letter is closest to the outside in that particular row or column. Fill the square!

       A   B   B       C
 +---+---+---+---+---+---+
A|   |   |   |   |   |   |
 +---+---+---+---+---+---+
 |   |   |   |   |   |   |D
 +---+---+---+---+---+---+
B|   |   |   |   |   |   |A
 +---+---+---+---+---+---+
C|   |   |   |   |   |   |D
 +---+---+---+---+---+---+
C|   |   |   |   |   |   |
 +---+---+---+---+---+---+
 |   |   |   |   |   |   |A
 +---+---+---+---+---+---+
   D       A   A   C