Given a $2$D matrix of characters grid containing the characters 'X', 'Y', and '.'.

Return the number of submatrices that include the top left cell grid[0][0], contain at least $1$ occurrence of 'X', and have an equal frequency of 'X' and 'Y'.

Constraints:

• $1 \leq$ grid.length, grid[i].length $\leq 1000$

• grid[i][j] is either 'X', 'Y', or '.'.

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