#!/usr/bin/env python
# -*- coding: utf-8 -*-


def CheckAns(i, S):
    if S[i] is '(':
        return 1
    else:
        return -1


def kakko(K, S):
    check = CheckAns(K - 1, S)
    i = K - 1

    if check is 1:
        while check is not 0:
            i += 1
            check += CheckAns(i, S)

    if check is -1:
        while check is not 0:
            i -= 1
            check += CheckAns(i, S)

    return i + 1


def main():
    N, K = map(int, input().split())
    S = input()

    print(kakko(K, S))


if __name__ == '__main__':
    main()