N,K=map(int,input().split())
S=list(input())
cnt=[0 for _ in range(N+1)]
prev="("
for i,s in enumerate(S):
    if s=="(":
        if prev=="(":cnt[i]=cnt[i-1]+1
        else:cnt[i]=cnt[i-1];prev="("
    else:
        if prev==")":cnt[i]=cnt[i-1]-1
        else:cnt[i]=cnt[i-1];prev=")"
v=cnt[K-1]
i=K
while i<N:
    if cnt[i]==v:
        print(i+1);exit()
    i+=1
i=K-2
while i>=0:
    if cnt[i]==v:
        print(i+1);exit()
    i-=1