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

print(ans)