import java.util.*;

public class _9252 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String a = sc.nextLine();
        String b = sc.nextLine();
        sc.close();

        int la = a.length(), lb = b.length();

        int[][] dp = new int[la+1][lb+1];

        for(int i=1; i<=la; i++) {
            for(int j=1; j<=lb; j++) {
                if(a.charAt(i-1) == b.charAt(j-1)) {
                    dp[i][j] = Math.max(dp[i-1][j-1] + 1, dp[i][j]);
                }
                else {
                    dp[i][j] = Math.max(dp[i][j], Math.max(dp[i-1][j], dp[i][j-1]));
                }
            }
        }

        System.out.println(dp[la][lb]);

        if(dp[la][lb] != 0) {
            int pa = la, pb = lb;
            String reverse = "";

            while(pa != 0 && pb != 0) {
                if(dp[pa-1][pb] == dp[pa][pb]) {
                    pa--;
                }
                else if (dp[pa][pb-1] == dp[pa][pb]){
                    pb--;
                }
                else {
                    reverse += a.charAt(pa-1);
                    pa--; pb--;
                }
            }

            String res = "";
            for(int i=dp[la][lb]-1; i >= 0 ; i--) res += reverse.charAt(i);

            System.out.println(res);
        }
    }
}