def main():
    N, K = map(int, input().split())
    S = input()
    if S[K-1] == ")":
        next_index = (K-1)-1
        count = 0
        while count != 1:
            if S[next_index] == "(":
                count += 1
            else:
                count -= 1
            next_index = next_index - 1
        # カウンタがすでに進んでいるので１を足し、
        # ０始まりから１始まりに直すために更に１を足す
        print(next_index + 2)
    else:
        next_index = (K-1)+1
        count = 0
        while count != 1:
            if S[next_index] == ")":
                count += 1
            else:
                count -= 1
            next_index = next_index + 1
        print(next_index)

if __name__ == '__main__':
    main()