More than Nim

A two-player game is played with two piles of stones, with sizes $$m,n$$. On a player's turn, that player can remove any positive integer number of stones from one pile, or the same positive integer number of stones from each pile. A player loses when they are unable to take a stone. If $$1 \leq m,n \leq 30$$, for how many of the $$30 \times 30 = 900$$ starting positions does the first player have a winning strategy?

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