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Problems

Rectangle

Rectangle

Time limit 2 seconds
Memory limit 64 MiB

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 (1m, n11).

Output data

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

Examples

Input example #1
2 2
Output example #1
6