Java题不会做，求解答过程，

Question

Answer 1

import java.util.Scanner;
public class Test01 {
    public static void main(String[] args) {
        Scanner input=new Scanner(System.in);
        int num,sum=0;
        for (int i=0;i<10;i++){
            num=input.nextInt();
            if (i%2==1){
                sum+=(num+2);
            }else {
                sum+=2*num;
            }
        }
        System.out.print(sum);
    }
}