class Dvach {
  static int reverse(int num) {
    if (num > -10 && num < 10) {
      return num;
    }

    String signed = String.valueOf(num % 10);
    num = Math.abs(num) / 10;

    return Integer.parseInt(signed + (reverse(num)));
  }

  public static void main(String[] args) {
    int[] testValues = {0, 1, -1, 21, 25659, -25659};
    for (int num: testValues) {
      System.out.println(reverse(num));
    }
  }    
}