StringBuilder buildResult = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            Character replace = s.charAt(i);
            if(Character.isUpperCase(replace)) {
                int newValue = 65 + (replace.charValue()%65 + k%26)%26;
                buildResult.append((char) newValue );
            }
            else if(Character.isLowerCase(replace)) {
                int newValue = 97 + (replace.charValue()%97 + k%26)%26;
                buildResult.append((char) newValue);
            } 
            else {buildResult.append(replace);}
        }
        return buildResult.toString();