public static boolean isPalindrome(String s){
    int start = 0, end = s.length() - 1;
     while(start < end){
      if(s.charAt(start) != s.charAt(end))
        return false;
      start++;
      end--;
      } 
    return true;
    }
  
  public static int palindromeIndex(String s) {
    int start = 0, end = s.length() - 1;

    if(isPalindrome(s))
      return -1;
    
    while(start < end){
      int start_elem = s.charAt(start);
      int end_elem = s.charAt(end);
      
      if(start_elem != end_elem){
        String s_without_start = s.substring(start + 1, end + 1);
        if(isPalindrome(s_without_start))
          return start;
      
        String s_without_end = s.substring(start, end);
        if(isPalindrome(s_without_end))
          return end;  
        }
      start++;
      end--;
      }
    
    return -1; 
  }