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

count = 1 #k番目の文字を＋1として同じ文字なら+1,違う文字なら-1する
if s[k-1] == "(":
    i = k
    while i <= n:
        if s[i] == "(":
            count += 1
        else:
            count -= 1
        
        if count == 0:
            print(i + 1)
            break
        else:
            i += 1

else:
    i = k - 2
    while i >= 0:
        if s[i] == ")":
            count += 1
        else:
            count -= 1
        
        if count == 0:
            print(i + 1)
            break
        else:
            i -= 1