Важная новость (битовые маски)

public static void main(String[] args)
         throws FileNotFoundException {
        Scanner in = new Scanner(new File("new2.in"));//new File("f.in")

        int n = in.nextInt();
        int k = in.nextInt();

        int maxv = (1 << n) - 1;

        int[] m = new int[n];
        for(int i = 0; i < n; i++)
        {
            m[i] = 1 << i;
        }
        int a, b;
        for (int i = 0; i < k; i++)
        {
            a = in.nextInt() - 1;
            b = in.nextInt() - 1;
            m[a] ^= 1 << b;
            m[b] ^= 1 << a;
        }

        int ans = n;
        for (int mask = (1 << n) - 1; mask >= 0; mask--)
        {
            int maskBitsCount = bitCount(mask);
            if (maskBitsCount >= ans)
                continue;

            int maskCopy = mask;
            int friendWhoKnow = 0;
            for (int i = 0; maskCopy != 0; maskCopy >>= 1, i++)
            {
                if ((maskCopy & 1) == 1)
                {
                    friendWhoKnow |= m[i];
                }
            }
            if (friendWhoKnow == maxv)
            {
                ans = maskBitsCount;
            }
        }
        System.out.println(ans);

    }