Elimination Game

    int lastRemaining(int n) {

        int res = 1, move = 1;

        bool left_right = true;

        while (n > 1)
        {
            if (left_right)
                res += move;
            else
                res += (n%2) ? move : 0;
            n /= 2;
            move *= 2;

            left_right = !left_right;
        }
        return res;

    }