N, K = map(int, raw_input().strip().split(" "))
K -= 1
S = raw_input()
if S[K] == "(":
    d = 1
    while d != 0:
        K += 1
        if S[K] == ")":
            d -= 1
        else:
            d += 1
    print(K + 1)
else:
    d = -1
    while d != 0:
        K -= 1
        if S[K] == ")":
            d -= 1
        else:
            d += 1
    print(K + 1)