public class stacktest {
	
	
	public static void main(String[]args){
		DoubleStack<Integer> stacks = new DoubleStack();
		int x = 0;
		boolean ok = true;
		while(x < 5){
			if(ok){
				stacks.pushA(x);
				ok = false;
			}else{
				stacks.pushB(x);
				ok = true;
			}
		}
		
		System.out.println(stacks.topA());
	}
}