import java.util.Scanner;


public class WordLadder {

    private String lastWord = "";

    public WordLadder() {
        Scanner scanner = new Scanner(System.in);
        while (true) {
            checkWord(scanner.readLine());
        }
    }

    public static void main(String[] args) {
        new WordLadder():
    }

    private void checkWord(String word) {
        if (word.length() == 0) {
            System.out.println();
            return;
        }
        System.out.println(word);
        if (lastWord.length() != 0 && word.length() != lastWord.length()) {
            System.out.println("Invalid word");
            return;
        }
        int occurrences = 0;
        char[] currWord = word.toCharArray();
        char[] lastWord = this.lastWord.toCharArray();
        for (int i = 0; i < currWord.length; i++) {
            for (int j = 0; j < lastWord.length; j++) {
                if (currWord[i] == lastWord[i]) {
                    occurrences++;
                }
            }
        }
        if (occurrences > 1) {
            System.out.println("Invalid word");
        } else {
            lastWord = word;
        }
    }

}