import std.stdio;

class Stack(T) {
  private T[] data;
  private int size;

  public this() {
    data = new T[16];
    size = 0;
  }

  public auto push(T thing) {
    if (size == data.length) {
      data.length *= 2;
    }
    data[size] = thing;
    size++;
  }

  public ref T top() {
    return data[size-1];
  }

  public auto pop() {
    size--;
    if (size < data.length/4) {
      data.length /= 2;
    }
  }
}

class Queue(T) {
  private Stack!T stack1;
  private Stack!T stack2;

  public this() {
    stack1 = new Stack!T();
    stack2 = new Stack!T();
  }

  public auto enqueue(T thing) {

  }

  public ref T front() {

  }

  public ref T back() {

  }

  public auto dequeue() {

  }
}

void main() {
    Stack!int thingy = new Stack!int;
  foreach(x; 1..100) {
    thingy.push(x);
  }
  writeln(thingy.top);
  thingy.pop();
  writeln(thingy.top);


}