n, k = map(int,input().split())
string = input()
cnt = 0
ans = 0

if string[k - 1] == "(":
    for i, w in enumerate(string[k-1:]):
        if w == "(" :
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0 :
            ans = k + i
            break

else:
    for i, w in enumerate(reversed(string[:k])):
        if w == ")":
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0 :
            ans = k - i
            break

print(ans)