public int MaxSightings(List<int> arr)
        {
            Dictionary<int, int> sightings = new Dictionary<int, int>();
            int maxSightings = 0;
            foreach (int i in arr)
            {
                if (sightings.ContainsKey(i))
                {
                    sightings[i]++;
                }
                else
                {
                    sightings[i] = 1;
                }

                maxSightings = Math.Max(maxSightings, sightings[i]);
            }

            int birdId = sightings.Where(kv => kv.Value == maxSightings).Min(kv => kv.Key);

            return birdId;

        }