求s=a+aa+aaa+aaaa+aa...a的值，其中a是一个数字。

import java.util.Arrays;
import java.util.Scanner;

class Demo{
	public static void main(String[] args){
		Scanner in = new Scanner(System.in);
		int sum = 0;
		System.out.println("input how many num to plus");
		int j = in.nextInt();
		System.out.println("input what num to plus");
		int num = in.nextInt();
		int n = 1;
		int[] c = new int[j];
		c[0] = 1;
		for(int i = 1;i