Captain crunch - ROT13 encoder program

The Captain Crunch decoder ring works by taking each letter in a string and adding 13 to it. For example, 'a' becomes 'n' and 'b' becomes 'o'. The letters "wrap around" at the end, so 'z' becomes 'm'.

This is what I've got after editing it a bit from peoples comments, but now it keeps telling me that output may have not been initialized and I have no clue why... also is there anything else I need to fix in my program?

In this case, I am only concerned with encoding lowercase characters

import java.util.Scanner;

public class captainCrunch {
 public static void main (String[] Args) {

 Scanner sc= new Scanner(System.in);
 String input;

 System.out.print("getting input");
 System.out.println("please enter word: ");
 input= sc.next();

 System.out.print(" ");
 System.out.print("posting output");
 System.out.print("encoding" + input + " results in: " + encode(input));
 }//end of main


 public static String encode(String input){

 System.out.print(input.length());
 int length= input.length();
 int index;
 String output;
 char c;
 String temp= " ";

        for (index = 0; index < length; index++) {

            c = input.charAt(index);
            if       (c >= 'a' && c <= 'm') c += 13;
            else if     (c >= 'n' && c <= 'z') c -= 13;
            output= temp + (char)(c);
        }
        return output;
    }

}