import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        int[] b = new int[n];
        // 遍历数组a
        for (int i = 0; i < n; i++) {
            String word = sc.next();
            b[i] = word.length();
            // 遍历字符串
            for (int j = 0; j < word.length(); j++) {
                int c = word.charAt(j) - 'a';
                a[i] |= 1 << c;
            }
        }
        int num = 0;
        for (int i = 0; i < a.length; i++) {
            for (int j = i; j < a.length; j++) {
                if ((a[i] & a[j]) == 0) {
                    num = Math.max(num, b[i] * b[j]);
                }
            }
        }
        System.out.println(num);
    }
}