N,K=map(int,input().split())
S=list(input())
cnt=1
if S[K-1]=="(":
    for i in range(K,N):
        if S[i]=="(":
            cnt+=1
        else:
            cnt-=1
        if cnt==0:
            print(i+1);exit()
elif S[K-1]==")":
    S.reverse()
    for i in range(N-K+1,N):
        if S[i]==")":
            cnt+=1
        else:
            cnt-=1
        if cnt==0:
            print(N-i);exit()