N,K=map(int,raw_input().split())
S=raw_input()
t={}
e=[0]*N
k=0
for i in xrange(N):
  if S[i]=="(":
    t[k]=[i]
    e[i]=k
    k+=1
  else:
    t[k-1].append(i)
    k-=1
    e[i]=k
a=t[e[K-1]]
print a[1]+1 if a[0]==K-1 else a[0]+1