import sys

n, k = map(int, sys.stdin.readline().rstrip().split())
s = sys.stdin.readline().rstrip()
parenthises = 0

if s[k - 1] == '(':
    for i, parenthisis in enumerate(s[k:]):
        if parenthisis == '(':
            parenthises += 1
        else:
            if parenthises == 0:
                print(k + i + 1)
                break
            else:
                parenthises -= 1
else:
    for i, parenthisis in enumerate(reversed(s[:k - 1:])):
        if parenthisis == ')':
            parenthises += 1
        else:
            if parenthises == 0:
                print(k - i - 1)
                break
            else:
                parenthises -= 1