from collections import deque
n,k = map(int,input().split())
s = input()
p = [-1] * n
st = deque([])
for i in range(n):
  if s[i] == '(':
    st.append(i)
  else:
    j = st.pop()
    p[i] = j
    p[j] = i
print(p[k - 1] + 1)