public static String waitAnswer(){
        while(true){
            try {
                String input = reader.readLine();
                if(input.matches("(^[a-h][1-8]$)|(^[9][9]$)|(^[0][0])$"))
                    return input;
                else{
                    Printer.invalidInput();
                    continue;
                }
            }
            catch(IOException e) {
                e.printStackTrace();
                System.exit(1);
            }
            break;
        }
        return null;
    }