Problems
Rectangle
Rectangle
Given rectangle m × n. To count the number of ways to split it into two parts, each of which is a connected set of unit cells.
For example, there are six ways to break this way a square 2 × 2, they are shown in the following figure.
Input data
The input file contains two integers m and n (1 ≤ m, n ≤ 11).
Output data
Derive the output file a single number - the required number of ways.
Examples
Input example #1
2 2
Output example #1
6