# -*- coding: utf-8 -*-
N, K = map(int, raw_input().split())
S = raw_input()
Slist = list(S)
left = []
for i in range(0, N):
    if Slist[i] == "(":
        left.append(i)
    elif Slist[i] == ")":
        tmp = left.pop()
        if i == K-1:
            print tmp + 1
            exit()
        elif tmp == K-1:
            print i + 1
            exit()