n,k = map(int,input().split())
s = input()
st = []
ans = []
for i in range(n):
    if s[i] == '(':
        st.append(i)
    else:
        t=st.pop()
        ans.append((t,i))

for i,j in ans:
    if i == k-1:
        print(j+1)
        break
    elif j == k-1:
        print(i+1)
        break