[java 백준] 실버 5/1292번 쉽게 푸는 문제

https://www.acmicpc.net/problem/1292

1292번: 쉽게 푸는 문제

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.StringTokenizer;
 
public class Main {
 
    public static void main(String[] args) throws NumberFormatException, IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int a = Integer.parseInt(st.nextToken());
        int b = Integer.parseInt(st.nextToken());
        int total = 0;
        ArrayList<Integer> arr = new ArrayList<Integer>();
        int i = 1;
        while (i <= 1000) {
            for (int j = 1; j <= i; j++) {
                arr.add(i);
            }
            i++;
        }
        for (int i1 = a - 1; i1 < b; i1++) {
            total += arr.get(i1);
        }
        System.out.println(total);
    }
 
}