n, k = map(int, input().split())
ans = [-1 for _ in range(n)]
lst = []
ss = input().rstrip()
for i, s in enumerate(ss, start = 1):
    if s == "(":
        lst.append(i)
    else:
        n = lst.pop(-1)
        ans[n - 1] = i
        ans[i - 1] = n
print(ans[k - 1])