백준 1292 Java 자바

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

1292번: 쉽게 푸는 문제

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import java.util.*;

 
public class Main {
 
	public static void main(String[] args){
			
		Scanner sc = new Scanner(System.in);
		int frst = sc.nextInt();
		int scd = sc.nextInt();
		int[] num=new int[scd];
		int j=1,res=0;
		for(int i=0;i<scd;) {
			for(int k=0;k<j;k++) {
				if(i>=scd)
					break;
				num[i++]=j;
			}
			j++;
		}
		for(int l=frst-1;l<=scd-1;l++) {
			res+=num[l];
		}
			
		System.out.println(res);
	}
	
}