def a(s):
    return 1 if s!=")" else -1

N,K=map(int,input().split())
S=input()

s=K-1
t=a(S[s])
e=s+t
c=t
while 1:
    c+=a(S[e])
    e+=t
    if c==0:
        break
print(1+e-t)