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

S = input()

s_stack = ['$']

for i in range(len(S)):
    if s_stack[-1] != '$':
        top_stack = s_stack[-1]
        if S[top_stack] == '(' and S[i] == ')':
            if top_stack == K-1:
                acording_point = i
                break
            elif i == K-1:
                acording_point = top_stack
                break
            s_stack.pop()
        else:
            s_stack.append(i)
    else:
        s_stack.append(i)

print(acording_point + 1)