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 = [-1] * n
for i, ss in enumerate(s):
    memo[i] = cnt
    if ss == '(':
        cnt += 1
    else:
        cnt -= 1
if s[k - 1] == '(':
    for i, v in enumerate(memo[::-1]):
        if memo[k - 1] == v:
            print(n - i - 1)
            break
else:
    for i, v in enumerate(memo):
        if memo[k - 1] == v:
            print(i)
            break