N,K=map(int, input().split())
S=input()
if S[K-1]=='(':
    a=S[K:]
    c=')'
    p=1
else:
    a=S[:(K-1)][::-1]
    c='('
    p=-1
w=1
n=0
for x in a:
    n+=p
    w+=(-1 if x==c else 1)
    if w==0:
        break
print(n+K)