N,K=map(int,(input().split()))
S=list(input())
C=1
if S[K-1]=='(':L,D=range(K,N),'('
else:L,D=reversed(range(0,K-1)),')'
for i in L:
 if S[i]==D:C+=1
 else:C-=1
 if C==0:
  print(i+1)
  break