
I am going to provide you with some code, the state of the environment, and the state of the concrete heap and abstract heap. The environment and heaps will be provided in JSON format. We just finished iteration number 1 of the loop on line 66. Please merge nodes in the heap to achieve the best balance of scalability and precision for detecting `TypeError: Cannot read properties of null or undefined`.
Here is the code: 

```javascript
const audio = document.querySelector("audio");
var songs = [
    {
      name: "Death of a Bachelor",
      cover:
        "https://chillhop.com/wp-content/uploads/2020/09/0255e8b8c74c90d4a27c594b3452b2daafae608d-1024x1024.jpg",
      artist: "Brendon Urie",
      audio: "doab.mp3",
      id: 0,
    },
    {
      name: "How to Save a Life",
      cover:
        "https://chillhop.com/wp-content/uploads/2020/07/ef95e219a44869318b7806e9f0f794a1f9c451e4-1024x1024.jpg",
      artist: "The Fray",
      audio: "htsal.mp3",
      id: 1,
    },
    {
      name: "Welcome to the Black Parade",
      cover:
        "https://chillhop.com/wp-content/uploads/2020/07/ff35dede32321a8aa0953809812941bcf8a6bd35-1024x1024.jpg",
      artist: "My Chemical Romance",
      audio: "wttbp.mp3",
      id: 2,
    },
  ];
  
var artists = [
  ];

function playSong(id) {
    var song = songs[id];
    audio.src = song.audio;
    audio.play();
}

function pauseSong() {
    audio.pause();
}

function addSong(name, cover, artist, id) {
    var song = {
        name: name,
        cover: cover,
        artist: artist,
        audio: name + ".mp3",
        id: id,
    };
    songs[id] = song;
}

function addArtist(name, genre, id) {
    var artist = {
        name: name,
        genre: genre,
        id: id,
    };
    artists[id] = artist;
}
addArtist("Brendon Urie", "pop", 0);
addArtist("The Fray", "rock", 1);
addArtist("My Chemical Romance", "punk", 2);

var n = getN();
for (var i = 3; i < n; i = i+1) {
    addSong("song" + i, "cover" + i + ".jpg", "artist" + i, i);
    addArtist("artist" + i, "genre" + i, i);
}
```

Here is the current state of the environment:
```json
{
  "audio": [
    "TOP"
  ],
  "n": [
    "TOP"
  ],
  "i": [
    3
  ],
  "songs": [
    "Abstract Address(3)"
  ],
  "artists": [
    "Abstract Address(4)"
  ]
}
```

Here is the current state of the concrete heap:
```json
{}
```

Here is the current state of the abstract heap:
```json
{
  "Abstract Address(0)": {
    "name": [
      "Death of a Bachelor"
    ],
    "cover": [
      "https://chillhop.com/wp-content/uploads/2020/09/0255e8b8c74c90d4a27c594b3452b2daafae608d-1024x1024.jpg"
    ],
    "artist": [
      "Brendon Urie"
    ],
    "audio": [
      "doab.mp3"
    ],
    "id": [
      0
    ]
  },
  "Abstract Address(1)": {
    "name": [
      "How to Save a Life"
    ],
    "cover": [
      "https://chillhop.com/wp-content/uploads/2020/07/ef95e219a44869318b7806e9f0f794a1f9c451e4-1024x1024.jpg"
    ],
    "artist": [
      "The Fray"
    ],
    "audio": [
      "htsal.mp3"
    ],
    "id": [
      1
    ]
  },
  "Abstract Address(2)": {
    "name": [
      "Welcome to the Black Parade"
    ],
    "cover": [
      "https://chillhop.com/wp-content/uploads/2020/07/ff35dede32321a8aa0953809812941bcf8a6bd35-1024x1024.jpg"
    ],
    "artist": [
      "My Chemical Romance"
    ],
    "audio": [
      "wttbp.mp3"
    ],
    "id": [
      2
    ]
  },
  "Abstract Address(3)": {
    "0": [
      "Abstract Address(0)"
    ],
    "1": [
      "Abstract Address(1)"
    ],
    "2": [
      "Abstract Address(2)"
    ],
    "3": [
      "Abstract Address(9)"
    ]
  },
  "Abstract Address(4)": {
    "0": [
      "Abstract Address(6)"
    ],
    "1": [
      "Abstract Address(7)"
    ],
    "2": [
      "Abstract Address(8)"
    ],
    "3": [
      "Abstract Address(10)"
    ]
  },
  "Abstract Address(5)": {
    "songs": [
      "Abstract Address(3)"
    ],
    "artists": [
      "Abstract Address(4)"
    ]
  },
  "Abstract Address(6)": {
    "name": [
      "Brendon Urie"
    ],
    "genre": [
      "pop"
    ],
    "id": [
      0
    ]
  },
  "Abstract Address(7)": {
    "name": [
      "The Fray"
    ],
    "genre": [
      "rock"
    ],
    "id": [
      1
    ]
  },
  "Abstract Address(8)": {
    "name": [
      "My Chemical Romance"
    ],
    "genre": [
      "punk"
    ],
    "id": [
      2
    ]
  },
  "Abstract Address(9)": {
    "name": [
      "song3"
    ],
    "cover": [
      "cover3.jpg"
    ],
    "artist": [
      "artist3"
    ],
    "audio": [
      "song3.mp3"
    ],
    "id": [
      3
    ]
  },
  "Abstract Address(10)": {
    "name": [
      "artist3"
    ],
    "genre": [
      "genre3"
    ],
    "id": [
      3
    ]
  }
}
```

Please provide an abstraction by merging nodes in the concrete and abstract heap, and provide a mapping between which nodes have been merged in your output. Only specify the addresses you want to merge.
