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

level, i = 1, 0

if S[K-1] == "(":
    while level != 0:
        if S[K+i] == "(":
            level += 1
        elif S[K+i] == ")":
            level -= 1
        i += 1
    ans = K+i

elif S[K-1] == ")":
    while level != 0:
        if S[K-2-i] == ")":
            level += 1
        elif S[K-2-i] == "(":
            level -=1
        i += 1
    ans = K-i

print ans