n, k = map(int, input().split())
s = str(input())
d = []
for i in range(n):
    if s[i] == '(':
        d.append(i+1)
    else:
        if d[-1] == k:
            print(i+1)
            exit()
        elif i+1 == k:
            print(d[-1])
            exit()
        else:
            d.pop()