Enemy choose a player from array ?

I'm trying to make my enemy pick a player from array that no enemy around him. Now, if player surrounded with 3 enemies, the rest will select second player closest to them. How to make enemy pick the second player ?

Code (CSharp):

1.  
2. public GameObject[] players;
3. public GameObject AttackThisPlayer;
4. public int player_number;
5. public bool PlayerSurrounded; // script attached to player, if 3 enemies around him it turn True.
6. public bool attackPlayer = false; // if enemy enter player zone turn true. So the rest will not pick this player.
7.  
8. void Start()
9. {
10.    players = GameObject.FindGameObjectsWithTag("Player"); // 5 players
11. }
12.  
13. void Update()
14. {
15.  
16.    for (int i = 0; i < player.Length; i++)
17.    {
18.        if (Vector3.Distance(transform.position, players[i].transform.position) <
19.            Vector3.Distance(transform.position, players[player_number].transform.position))
20.        {
21.            player_number =  i;
22.            AttackThisPlayer = players[player_number];
23.  
24.        }
25.    }
26.  
27.    PlayerSurrounded = AttackThisPlayer.GetComponentInChildren<enemy_around>().enemiesBool;
28.  
29.   }
30.  
31.     void OnTriggerEnter(Collider other)
32.     {
33.         if (other.transform.CompareTag("Player") )
34.         {
35.         attackPlayer = true;
36.         }
37.  
38.     }
39.  
40.     void OnTriggerExit(Collider other)
41.     {
42.         if (other.transform.CompareTag("Player"))
43.         {
44.                 attackPlayer = false;
45.         }
46.     }
47.  
48. }
49.