cse16218_ex2_10.py

def depth(s, n): 
    current_max = 0
    final_max = 0
    
    for i in range(n): 
        if s[i] == '(': 
            current_max += 1
  
            if current_max > final_max: 
                final_max = current_max 
        elif s[i] == ')': 
            if current_max > 0: 
                current_max -= 1
            else: #unbalanced
                return -1
                
    if current_max != 0: #unbalanced
        return -1
  
    return final_max
  
s = input()
print (depth(s, len(s)))