def min_operations(s):
    n = len(s)
    required_conversions = 0
    
    for i in range(n):
        for j in range(i+1, n):
            substring = s[i:j+1]
            zeros = substring.count('0')
            ones = len(substring) - zeros
            
            if zeros >= ones:
                required_conversions = max(required_conversions, zeros - ones + 1)
    
    if required_conversions > s.count('0'):
        return -1
    
    return required_conversions