N, K = map(int, raw_input().split())
s = raw_input()
dx = 1  #left to right
if s[K-1] == ')':
    dx = -1
i = K-1
cnt = 1 #(num of same bracket as s[K-1]) - (not same)
while cnt != 0:
    i += dx
    if s[i] == s[K-1]:
        cnt += 1
    else:
        cnt -= 1
print i+1