先找出a1,然后输出

import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int input = sc.nextInt();
            // a1 = ( n -1 ) * n + 1
            StringBuilder sb =new StringBuilder();
            int a1 = input * input - input + 1;
            sb.append(a1);
            for(int i = 1;i<input;i++){
                a1 = a1 + 2;
                sb.append("+");
                sb.append(a1);
            }
            System.out.println(sb.toString());
        }
    }
}