Peaceful Rooks#3446
A rook is a chess piece that moves along ranks and files.
Let us consider white rooks and black rooks on an m \times n chessboard. We call the arrangement of the rooks on the chessboard peaceful if no white rook attacks a black one (and vice-versa).
Given , , and , find the number of peaceful arrangements of the rooks on the chessboard.
The input file contains four integer numbers: , , and (2 \le m, n \le 10, 1 \le k, 1 \le l, k + l \le m \cdot n).
Output one integer number - the number of peaceful arrangements of white and black rooks on the m \times n chessboard.
Example 1