from collections import deque

n, k = map(int, input().split())
S = input()

Que = deque()
for i in range(n):
    if S[i] == '(':
        Que.append(i)
    else:
        f = Que.pop()
        if i + 1 == k:
            print(f + 1)
            break
        elif f + 1 == k:
            print(i + 1)
            break