n, k = map(int, input().split())
s = input()
x = 0
idx = {}
idx[0] = 0
for i in range(n):
    if s[i] == '(':
        x += 1
        idx[x] = i + 1
    else:
        x -= 1
        if i + 1 == k:
            print(idx[x] + 1)
            break
        if idx[x] + 1 == k:
            print(i + 1)
            break
        idx[x] = i + 1