Minimize Marbles in Grid

You have a grid grid[][] containing characters 'X' and 'O'. 'X' represents marbles. You can remove a marble if there are other marbles in the same row or column. The goal is to minimize the number of marbles left in the grid. Implement a function to compute the minimum number of marbles remaining. Example Input 4 XOXX OXOX XOOX XXOX