from collections import deque

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

d = deque()
for i in range(N):
    if S[i] == "(":
        d.append(i+1)
    else:
        n = d.pop()
        if K == i+1:
            print(n)
            break
        elif K == n:
            print(i+1)
            break