N, K = map(int, input().split())
s = str(input())
k = s[K - 1]
pos = 0
if k == '(':
    for j in range(1, N - K + 1):
        if s[K - 1 + j] != k and pos == 0:
            print(K + j)
            break
        elif s[K - 1 + j] == k:
            pos += 1
        else:
            pos -= 1
else:
    for i in range(1, K):
        if s[K -1 -i] != k and pos == 0:
            print(K - i)
            break
        elif s[K -1 -i] == k:
            pos += 1
        else:
            pos -= 1