# -*- coding: utf-8 -*-
"""
No.22 括弧の対応
https://yukicoder.me/problems/no/22

"""
import sys
from sys import stdin
input = stdin.readline


def solve(K, S):
    res = [0] * (len(S)+1)
    status = []
    for i, s in enumerate(S, start=1):
        if s == '(':
            status.append(i)
        elif s == ')':
            try:
                t = status.pop()
            except:
                return 0
            res[i] = t
            res[t] = i
    return res[K]


def main(args):
    N, K = map(int, input().split())
    S = input().strip()
    ans = solve(K, S)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])