import sys

sys.setrecursionlimit(10 ** 8)

input = sys.stdin.readline


def main():
    N, K = [int(x) for x in input().split()]
    S = input().strip()

    if S[K - 1] == "(":
        cnt = 1
        for i in range(K, N):
            if S[i] == "(":
                cnt += 1
            else:
                cnt -= 1
                if cnt == 0:
                    print(i + 1)
                    return
    else:
        cnt = 1
        for i in range(K - 2, -1, -1):
            if S[i] == ")":
                cnt += 1
            else:
                cnt -= 1
                if cnt == 0:
                    print(i + 1)
                    return




if __name__ == '__main__':
    main()