N, K = map(int, input().split())
S = list(input())
stuck = []
if S[K - 1] == "(":
    start = K
    finish = N
    INC = 1
else:
    start = K - 2
    finish = -1
    INC = -1
stuck.append(S[K - 1])
for i in range(start, finish, INC):
    if stuck[-1] != S[i]:
        stuck.pop()
    else:
        stuck.append(S[i])
    if not stuck:
        print(i + 1)
        break