в чем проблема?
package com.javarush.task.task04.task0442;
import java.io.BufferedReader;
import java.io.InputStreamReader;
/*
Суммирование
*/
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader BR = new BufferedReader( new InputStreamReader(System.in));
int sum = 0;
while (true){
int num = Integer.parseInt(BR.readLine());
if (num == -1){
break;
}sum+=num;
System.out.println(sum);
}
}
}