N,K = map(int,input().split())
S = [""]+list(input())

init = S[K]
index = K
cnt = 1
if init==")":
    bct = -1
else:
    bct = 1

while True:
    index += bct
    if init==S[index]:
        cnt+=1
    else:
        cnt-=1
    if cnt==0:
        break
print(index)