from heapq import heappop,heappush
N,K = map(int,input().split())
K -= 1
S = input()
P = [-1] * N
heap = []
cnt = 1
for i in range(N):
    if S[i] == '(':
        P[i] = cnt
        heappush(heap, -(cnt))
        cnt += 1
    else:
        P[i] = -heappop(heap)
for i in range(N):
    if P[i] == P[K] and i != K:
        print(i+1)
        break