------
## 最终结论
```python
def minNumberOfFrogs(croakOfFrogs: str) -> int:
    count = {'c': 0, 'r': 0, 'o': 0, 'a': 0, 'k': 0}
    frogs = 0
    max_frogs = 0
    
    for char in croakOfFrogs:
        if char not in count:
            return -1
        
        count[char] += 1
        
        if char == 'c':
            frogs += 1
            max_frogs = max(max_frogs, frogs)
        elif char == 'k':
            frogs -= 1
            
        # Check the order of the characters
        if count['r'] > count['c'] or count['o'] > count['r'] or count['a'] > count['o'] or count['k'] > count['a']:
            return -1
    
    # Check if all counts are zero at the end
    if any(count[char] != (count['c'] if char == 'c' else 0) for char in 'croak'):
        return -1

    return max_frogs
```