n, k = map(int, input().split())
k -= 1
s = input()
flipped = s[k] == ')'
if flipped:
    s = ''.join('()'[c == '('] for c in reversed(s))
    k = n - 1 - k
depth = 1
for i in range(k + 1, n):
    if s[i] == ')':
        depth -= 1
    else:
        depth += 1
    if depth == 0:
        break
if flipped:
    i = n - 1 - i
print(i + 1)