def main():
    N,K = map(int, input().split())
    S = list(input())
    K = K-1
    count = 0

    for i in range(N):
        if S[i] == ')':
            count = i
            while S[count] != '(':
                count -= 1
            if count == K:
              print(i + 1)
              return
            elif i == K:
              print(count + 1)
              return
            
            S[i] = '0'
            S[count] = '0'



if __name__=='__main__':
  main()