public static void main(String[] args) throws Exception {
        int[] arg = { 0, 0 };
        for (int i = 0; i < 2; i++) {
            System.out.print("输入第" + (i + 1) + "个数:");
            DataInputStream di = new DataInputStream(System.in);
            String num = di.readLine();
            arg[i] = Integer.parseInt(num);
        }
        System.out.println(firstMethod(arg[0], arg[1]));
        System.out.println(secondMethod(arg[0], arg[1]));
    }

    static int firstMethod(int start, int end) {
        int sum = 0;
        for (; start <= end; start++) {
            sum += start;
        }
        return sum;
    }

    static int oneToAnum(int num) {
        int k = ((1 + num) * num) / 2;
        return k;
    }

    static int secondMethod(int first, int second) {
        return oneToAnum(second) - oneToAnum(first - 1);
    }