Two positive integer m, n (0 < m, n < 10) per line. Two zeros indicate the end of input.

内存限制：128 MiB 时间限制：1 Sec

Given an m*n grid, you're required to fill it with the numbers from 1 to m*n but the following rules should be satisfied:

1. each number in grid is larger than its above;

2. each number in grid is larger than its left.

Now, I wonder how many distinct solutions I could make on a grid.

For example. Consider such a 2*3 grid, we have the following solutions:

```
123 124 134 135 125
456 356 256 246 346
```

Thus, the sum is 5.

Two positive integer m, n (0 < m, n < 10) per line. Two zeros indicate the end of input.

A single integer per line for each case -- the number of distinct solutions.

```
2 3
```

0 0

```
```

5

本题为多组数据，请做到"0 0"结束