n, k = [int(x) for x in input().split()]
s = input()
stk = list()

for i, c in enumerate(list(s)):
    if c == "(":
        stk.append([i, c])
    else:
        j = stk.pop()

        if i == k - 1:
            print(j[0] + 1)
            break
        elif j[0] == k - 1:
            print(i + 1)
            break