//David Goldman
//School: Freehold High School
//School Code : 3001
//Senior Divison
//Mr. Gill
//Contest 2
//ACSL Bits


package Contest_2;

import java.util.*;

public class DG_Bits {
	public static void main(String[] args)
	{
		Scanner scanLine = new Scanner(System.in);
		ArrayList<String> origStrings = new ArrayList<String>();
		for (int i =0; i < 5; ++i)
		{
			System.out.println((i+1) + ". ");
			String line = scanLine.nextLine();
			Scanner thisLine = new Scanner(line.replaceAll(",", " "));
			int numOf = thisLine.nextInt();
			String firstLine = thisLine.next();
			origStrings.add(firstLine);
			char[] arr = firstLine.toCharArray();
			for (int curString = 2; curString <= numOf; ++curString)
			{
				String cur = thisLine.next();
				if (!origStrings.contains(cur))
					origStrings.add(cur);
				for (int charIndex = 0; charIndex < arr.length; ++charIndex){
					if (arr[charIndex] !=cur.charAt(charIndex))
						arr[charIndex] = '*';
				}
			}
			String bitString = new String(arr);
			int times = timesCharInString('*',bitString);
			if (Math.pow(2, times) == origStrings.size()) 
					System.out.println(bitString) ;
			else System.out.println("NONE");
			origStrings.clear();
		}
	}
	public static int timesCharInString(char c, String s)
	{
		int numOf = 0;
		for (char character : s.toCharArray())
		{
			if (character == c)
				++numOf;
		}
		return numOf;
	}
}