N, K = map(int, input().split(' '))
cnt = 0
t = [0 for i in range(N)]
for i, s in enumerate(input()):
    if s == '(':
        cnt += 1
    t[i] = cnt
    if s == ')':
        cnt -= 1
tmp = t[K-1]
t[K-1] = 0
print(t.index(tmp) + 1)