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import java.io.*;
import java.util.Arrays;
import java.util.Collections;
import java.util.StringTokenizer;

public class R455A {

    FastScanner sc;
    PrintWriter out;

    String firstName;
    String lastName;


    public void solve()  {
        char[] a = sc.next().toCharArray();
        char[] b = sc.next().toCharArray();


        Arrays.sort(a);
        Arrays.sort(b);

        out.println(a[0] + "" + b[0]);

        // out.println("hello");
        //out.println(firstName.charAt(0) + "" + firstName.charAt(1) + "" + lastName.charAt(0));
    }

    private void run() {
        //sc = new FastScanner(new File("input.txt"));
         sc = new FastScanner(System.in);
        out = new PrintWriter(System.out);
        //int test = 1;
        //for (int i=1; i<=test; i++) {
            //System.out.println("test #" + i);
            solve();
            //System.out.println();
        //}

        out.close();
    }

    public static void main(String[] args) {
        new R455A().run();
    }

    private class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        FastScanner(File f) {
            try {
                br = new BufferedReader(new FileReader(f));
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
        }

        FastScanner(InputStream f) {
            br = new BufferedReader(new InputStreamReader(f));
        }

        String next() {
            while (st == null || !st.hasMoreTokens()) {
                String s = null;
                try {
                    s = br.readLine();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (s == null)
                    return null;
                st = new StringTokenizer(s);
            }
            return st.nextToken();
        }

        boolean hasMoreTokens() {
            while (st == null || !st.hasMoreTokens()) {
                String s = null;
                try {
                    s = br.readLine();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (s == null)
                    return false;
                st = new StringTokenizer(s);
            }
            return true;
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }
    }
}