# coding: utf-8

N,K = map(int,input().split(" "))
K -= 1
S = input().strip()
res = 0
stack = []
for i in range(N):
    if S[i] == "(":
        if i == K:
            stack.append((i,S[i],'*'))
        else:
            stack.append((i,S[i]))
    else:
        p = stack.pop()
        if '*' in p:
            res = i+1
        if i == K:
            res = p[0]+1

print(res)