N, K = map(int, input().split())
from collections import deque
st = deque()
S = input()
K -= 1
for i in range(N):
    if S[i] == ")":
        top = st.pop()
        if top[0] == "(":
            if K == i:
                print(top[1] + 1)
                exit()
            elif K == top[1]:
                print(i + 1)
                exit()
        else:
            st.append(top)
            st.append((S[i], i))
    else:
        st.append((S[i], i))