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

Q = []
for i in range(N):
    if S[i] == '(':
        Q.append(i)
    else:
        r = Q.pop()
        if K-1 == r:
            print(i+1)
            exit()
        elif K-1 == i:
            print(r+1)
            exit()