N,K = map(int, raw_input().split())
S = raw_input()
K-=1
dif=1
if S[K] == ')':
   dif = -1
while dif != 0:
   K += dif/abs(dif)
   if S[K] == ')':
      dif -=1
   else:
      dif +=1
print K+1