n, k = map(int, input().split())
s = input()

if s[k-1] == '(':
    cnt = 1
    for i, p in enumerate(s[k:]):
        cnt += 1 if p == '(' else -1
        if cnt == 0:
            result = k + i + 1
            break
else:
    cnt = -1
    for i, p in enumerate(s[k-2::-1]):
        cnt += 1 if p == '(' else -1
        if cnt == 0:
            result = k - i - 1
            break
print(result)