Hello,
How can my program get AC even it returns wrong answer for the first test?

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;


public class SandrosBook {

    public static void main(String args[]) throws IOException{

        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);

        PrintWriter out=new PrintWriter(System.out);

        int[] a=new int[26];

        String s=br.readLine();
        int i=1;
        int start=0,end=0;
        start=s.charAt(0)-97;
        int max=0;




        while(i<s.length()){
            char c=s.charAt(i);
            a[(int)c-97]++;
            i++;
        }

        int k=0;
      for(int ii=0;ii<26;ii++){
           if(a[ii]>max)
           {
           max=a[ii];
           k=ii;
           }
        }

           k=k+97;

        System.out.println((char)k);
        out.flush();
    }

}