n, k = map(int, input().split())
s = input()

cnt = 1
if s[k-1] == "(":
    for i in range(k, n):
        if s[i] == "(":
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0:
            print(i + 1)
            break
else:
    s = s[::-1]
    for i in range(n-k+1, n):
        if s[i] == ")":
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0:
            print(n - i)
            break