N, K = map(int, input().split())
K -= 1
S = input()

stack = []
for i, s in enumerate(S):
    if s == '(':
        stack.append(i)
    else:
        l = stack.pop()
        if i == K:
            print(l + 1)
            break
        elif l == K:
            print(i + 1)
            break