------
## 最终结论
```python
def findMinStep(board, hand):
    from collections import Counter

    def remove_consecutive(s):
        i = 0
        while i < len(s):
            j = i
            while j < len(s) and s[j] == s[i]:
                j += 1
            if j - i >= 3:
                return remove_consecutive(s[:i] + s[j:])
            i = j
        return s

    def dfs(board, hand_count):
        board = remove_consecutive(board)
        if not board:
            return 0
        if not any(hand_count.values()):
            return float('inf')
        
        min_steps = float('inf')
        i = 0
        while i < len(board):
            j = i
            while j < len(board) and board[j] == board[i]:
                j += 1
            
            needed_balls = max(0, 3 - (j - i))
            
            if hand_count[board[i]] >= needed_balls:
                hand_count[board[i]] -= needed_balls
                min_steps = min(min_steps, needed_balls + dfs(board[:i] + board[j:], hand_count))
                hand_count[board[i]] += needed_balls
            
            i = j
        
        return min_steps

    hand_count = Counter(hand)
    result = dfs(board, hand_count)
    return result if result != float('inf') else -1

# Examples:
print(findMinStep("WRRBBW", "RB")) # Output: -1
print(findMinStep("WWRRBBWW", "WRBRW")) # Output: 2
print(findMinStep("G", "GGGGG")) # Output: 2
print(findMinStep("RBYYBBRRB", "YRBGB")) # Output: 3
```