#3021

Alice and Bob Playing Flower Game

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math

Description

Alice and Bob are playing a turn-based game on a field, with two lanes of flowers between them. There are x flowers in the first lane between Alice and Bob, and y flowers in the second lane between them.

The game proceeds as follows:

- Alice takes the first turn.

- In each turn, a player must choose either one of the lane and pick one flower from that side.

- At the end of the turn, if there are no flowers left at all in either lane, the current player captures their opponent and wins the game.

Given two integers, n and m, the task is to compute the number of possible pairs (x, y) that satisfy the conditions:

- Alice must win the game according to the described rules.

- The number of flowers x in the first lane must be in the range [1,n].

- The number of flowers y in the second lane must be in the range [1,m].

Return the number of possible pairs (x, y) that satisfy the conditions mentioned in the statement.

Example 1:

Input: n = 3, m = 2
Output: 3
Explanation: The following pairs satisfy conditions described in the statement: (1,2), (3,2), (2,1).

Example 2:

Input: n = 1, m = 1
Output: 0
Explanation: No pairs satisfy the conditions described in the statement.

Solution