N,K=map(int,raw_input().split())
S=raw_input()
Slist=list(S)

num=1
num2=-1
if Slist[K-1]=='(':
    for i in xrange(N-K):
        if Slist[K+i]=='(':
            num+=1
        elif Slist[K+i]==')':
            num-=1
        if num==0:
            print(K+i+1)
            break
elif Slist[K-1]==')':
    for i in xrange(K-1):
        if Slist[K-2-i]==')':
            num2-=1
        elif Slist[K-2-i]=='(':
            num2+=1
        if num2==0:
            print(K-i-1)
            break