import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

n, k = map(int, readline().split())
s = readline().rstrip().decode()
cnt = 0
memo = [0] * n
for i, ss in enumerate(s):
    if ss == ')':
        memo[i] = cnt
        cnt -= 1
    else:
        cnt += 1
        memo[i] = cnt
if s[k - 1] == '(':
    for i, ss in enumerate(memo[k:]):
        if ss == memo[k - 1]:
            print(k + i + 1)
            break
else:
    for i, ss in enumerate(memo[:k - 1][::-1]):
        if ss == memo[k - 1]:
            print(k - i - 1)
            break