N, K = map(int, raw_input().split())
s = raw_input()
cnt = 0
if s[K-1] == ")":
    s = s[:K]
    for i in reversed(xrange(len(s))):
        if s[i] == ")":
            cnt += 1
        if s[i] == "(":
            cnt -= 1
        if cnt == 0:
            print i+1
else:
    s = s[K-1:]
    for i in xrange(len(s)):
        if s[i] == "(":
            cnt += 1
        if s[i] == ")":
            cnt -= 1
        if cnt == 0:
            print i + K