n,k = map(int,input().split())
s = input()
st = []
for i,si in enumerate(s):
    i += 1
    if st and st[-1][0] == "(" and si == ")":
        if i == k:
            ans = st[-1][1]
            break
        elif st[-1][1] == k:
            ans = i
            break
        else:
            st.pop()
    else:
        st.append((si,i))

print(ans)