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

The input file contains two integers m and n (1 ≤ m, n ≤ 11).

Output

Derive the output file a single number - the required number of ways.

Examples