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