public class EnigmaUno {

   public static void main(String[] args) {
      System.out.println("E1: " + enigma(2, 8));
      System.out.println("E2: " + enigma(2, 9));
      System.out.println("E3: " + enigma(3, 4));
      System.out.println("E4: " + enigma(2, -1));
   }

   public static double enigma(double x, int n) {
      if (n < 0)
         return 1.0 / enigma(x, -n);
      else if (n == 0)
         return 1.0;
      else if (n % 2 == 0) {
         double parcial = enigma(x, n / 2);
         return parcial * parcial;
      } else {
         double parcial = enigma (x, (n - 1) / 2);
         return parcial * parcial * x;
      }
   }

}