All the Rectangles

Difficulty: 1200 2000 ms 128 MB

math combinatorics

How many axis-aligned rectangles (of any size) does an N×M grid contain?

Input: one line with two integers N and M.

Output: C(N+1, 2) · C(M+1, 2).

Constraints:

• 1 ≤ N, M ≤ 10⁵

Sample Tests

2 2

9

1 1

1

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