N, K = map(int, raw_input().split())
S = raw_input()

match = [-1 for _ in xrange(N)]
stack = []

for i, c in enumerate(S):
    if c == '(':
        stack.append(i)
    else:
        j = stack.pop()
        match[i] = j + 1
        match[j] = i + 1

print match[K - 1]