String Distance Replacement

import java.lang.;
import java.io.;
import java.util.*;
import java.util.Scanner;

public class vk{
public static void main(String [] args)
{
Scanner sc=new Scanner(System.in);
String s=sc.nextLine();
int a;
String s1="";
for(int i=0;i<s.length()-1;i++)

 {
     char t;
     char c=s.charAt(i);
     s1+=c;
     a=s.charAt(i)-96+s.charAt(i+1)-96;
     if(a>26)
     {
         a=a%26;
     }
     int b;
     b=96+a;
      t=(char)b;
      s1+=t;
      if(s1.length()-1>s.length()){
      s1+=s.charAt(i+1);
     System.out.println(s1);}

 }

 
}

}

input:board
output:bqopasrvd