n, k = map(int, input().split())
s = input()
k -= 1
s_l = []
count = 0
for i in range(n):
    if s[i] == '(':
        s_l.append(count)
        count += 1
    else:
        count -= 1
        s_l.append(count)

ans = [i for i, x in enumerate(s_l) if x == s_l[k]]
if k == ans[0]:
    print(ans[-1] + 1)
else:
    print(ans[0] + 1)