暴力枚举

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[][] arr = new int[n][27];

        for (int i = 0; i < arr.length; i++) {
            String str = sc.next();
            arr[i][26] = str.length();
            for (int j = 0; j < str.length(); j++) {
                arr[i][str.charAt(j) - 'a']++;
            }
        }
        int ans = 0;
        Arrays.sort(arr, (o1, o2) -> (o2.length - o1.length));
        for (int i = 0; i < arr.length; i++) {
            int j = i + 1;
            for (; j < arr.length; j++) {
                if(!cal(arr[i], arr[j])){
                    ans = Math.max(ans, arr[i][26] * arr[j][26]);
                }
            }
        }
        System.out.println(ans);
    }
    public static boolean cal(int[] a, int[] b){
        for (int i = 0; i < 26; i++) {
            if(a[i] > 0 && b[i] > 0) return true;
        }
        return false;
    }
}