hara

https://www.acmicpc.net/problem/2921 import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; public class a2921 { public static void main(String[] args) throws NumberFormatException, IOException { BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); int num=Integer.parseInt(br.readLine()); int sum=0; for(int i=0; i=i;j--){ sum+=(i+j); } } S..