N, K = map(int, input().split())
S = input()
x = 1
i = 1
if S[K-1] == ')':
    while x != 0:
        if S[K-1-i] == ')':
            x += 1
        else:
            x -= 1
        i += 1
    print(K - i + 1)
else:
    while x != 0:
        if S[K-1+i] == '(':
            x += 1
        else:
            x -= 1
        i += 1
    print(K + i - 1)