N, K = map(int, input().split())

S = input()

x = 0


if S[K - 1] == '(':
    
    for i in range(K, N):
        
        if S[i] == ')':
            
            if x == 0:
                
                print(i + 1)
                break
                
            else:
                
                x -= 1
                
        else:
            
            x += 1
            
else:
    
    for i in range(K - 2, -1, -1):
        
        if S[i] == '(':
            
            if x == 0:
                
                print(i + 1)
                
                break
            
            else:
                
                x -= 1
                
        else:
            
            x += 1