using System;
using System.Collections.Generic;
using System.Linq;

namespace Problem_2___Shoot_for_the_Win_03_Mid_Exam_Retake
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> targets = Console.ReadLine()
                .Split()
                .Select(int.Parse)
                .ToList();

            string index = Console.ReadLine();
            int count = 0;

            while (index != "End")
            {
                int newIndex = int.Parse(index);

                //if (newIndex > targets.Count - 1)
                // Every time you receive an index, you need to shoot the target on that index, 
                // if it is possible. + you can't shoot a target, which is already shot.
                if (newIndex < 0 || newIndex >= targets.Count || targets[newIndex] == -1)
                {
                    // new index is taken from the Console and continue triggers a
                    // new iteration in the while loop
                    index = Console.ReadLine();
                    continue;
                }

                int oldValue = targets[newIndex];
                //int oldValue = targets[newIndex];
                //targets.RemoveAt(newIndex);
                //targets.Insert(newIndex, -1);

                targets[newIndex] = -1;
                count++;
                for (int i = 0; i <= targets.Count - 1; i++)
                {
                    if (targets[i] == -1)
                    {
                        // Keep in mind that you can't shoot a target, which is already shot. 
                        // You also can't increase or reduce a target, which is considered shot.
                        continue;
                    }

                    if (oldValue < targets[i])
                    {

                        int newValue = targets[i] - oldValue;
                        // targets[i] directly modifies value in List collection
                        targets[i] = newValue;


                        //targets.RemoveAt(i);
                        //targets.Insert(i, newValue);
                    }
                    else if (oldValue >= targets[i] && targets[i] != -1)
                    {
                        int newValue = oldValue + targets[i];
                        targets[i] = newValue;

                        //targets.RemoveAt(i);
                        //targets.Insert(i, newValue);
                    }

                }
                index = Console.ReadLine();
            }

            Console.Write($"Shot targets: {count} -> {string.Join(" ", targets)}");
        }
    }
}

Здравейте, не намерих решение на JAVA, и ще се радвам да разяснение. 

Това е кодът.Shoot for the win - Pastebin.com

2рият вход излиза, но проблемът е с първия вход.

4упи се на ред 28, при подаване за втори път на индекс. ( да, той е извън size-a, но преди това има проверка за невалиден индекс.)

Мерси