public static int migratoryBirds(List<Integer> arr) {
        int max = Integer.MIN_VALUE;
        int count = 0;
        int idMin = Integer.MAX_VALUE;
        int id = 0;
        
        Collections.sort(arr);
        
        for (int i = 0, j = 1; j < arr.size() - 1; i++, j++) {
            if (arr.get(i) == arr.get(j + 1)) {
                id = arr.get(i);
                count++;
                if (count > max) {
                    max = count;
                    idMin = id;
                }
            } else {
                count = 0;
            }
        }
        return idMin;
    }