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