How To Get Index Of Array Based On User Inputted Account Number

In my account driver I am trying to get the user inputted account number to get the account by account number. In my code

System.out.println("Which Account number: "); int account = scan.nextInt();
ac.get(account-1);

This works if my accounts are numbered incrementally starting with one, I want it to match the inputted account number

System.out.println("Account number: "); int num = scan.nextInt();

I am thinking a for loop is probably needed. Here is my code:

public class AccountDriver {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
ArrayList<Account> ac = new ArrayList<>();
boolean more=true;
boolean again=false;

[code]....