public class DoubleStack {

   public static void main (String[] argum) {
      // TODO!!! Your tests here!
   }

   DoubleStack() {
      // TODO!!! Your constructor here!
   }

   @Override
   public Object clone() throws CloneNotSupportedException {
      return this; // TODO!!! Your code here!
   }

   public boolean stEmpty() {
      return false; // TODO!!! Your code here!
   }

   public void push (double a) {
      // TODO!!! Your code here!
   }

   public double pop() {
      return 0.; // TODO!!! Your code here!
   } // pop

   public void op (String s) {
      // TODO!!!
   }
  
   public double tos() {
      return 0.; // TODO!!! Your code here!
   }

   @Override
   public boolean equals (Object o) {
      return true; // TODO!!! Your code here!
   }

   @Override
   public String toString() {
      return null; // TODO!!! Your code here!
   }

   public static double interpret (String pol) {
      return 0.; // TODO!!! Your code here!
   }

}