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

class Program
{
    private static void Main()
    {
        Bag bag = new Bag(100);
    }
}

class Bag
{
    private List<Cell> _cells;

    public int MaxWeidth { get; private set; }
    public int Weidth => _cells.Sum(cell => cell.Count);
    public IReadOnlyCollection<Cell> Cells => _cells;


    public Bag(int maxWeidth, IEnumerable<Item> items)
    {

        foreach (var item in items)
            _cells.Add(new Cell(item));

        MaxWeidth = maxWeidth;
    }

    public void AddItem(Item item, int count)
    {
        Cell cell = _cells.FirstOrDefault(x => x.Item == item);

        if (cell.Item == null)
            throw new InvalidOperationException();

        if (Weidth + count > MaxWeidth)
            throw new InvalidOperationException();

        cell.Count += count;
    }

    public class Cell
    {
        public readonly Item Item;
        public int Count;

        public Cell(Item item)
        {
            Item = item;
            Count = 0;
        }
    }
}

class Item
{
    public string Name;
}