SortedContainer.cs

public class Container
{
    private SortedDictionary<int, int> _storage = new();
    private int _count = 0;

    public Container()
    {
        // write your code here
    }

    public void Add(int value)
    {
        _count++;
        _storage.TryGetValue(value, out var count);
        _storage[value] = count + 1;
    }

    public bool Delete(int value)
    {
        if (!_storage.TryGetValue(value, out var count))
            return false;

        _count--;

        if (count == 1)
            return _storage.Remove(value);

        _storage[value] = count - 1;

        return true;
    }

    public int GetMedian()
    {
        if (_count == 0)
            throw new InvalidOperationException();

        int index;
        if (_count % 2 == 0)
            index = _count / 2;
        else
            index = _count / 2 + 1;

        foreach (var (k, v) in _storage)
        {
            if (index <= v)
                return k;
            index -= v;
        }

        return 0;
    }
}