public int rowAfterDrop(int[][] board, int col){
        if(col > board[0].length - 1 || col < 0) //if col is more then the number of columns or negative
        {
            return -1;
        }
        for(int i = board.length - 1; i >= 0; i--) //for each row
        {
            if(board[i][col] == 0) //in the selected column, if it's empty
            {
                return i; //return the row to drop in
            }
        }

        return -1;
    }
}