import java.util.ArrayList;
public class stackb {
static class stack {
static ArrayList list = new ArrayList<>();
//isEmpty
public static boolean isEmpty(){
return list.size() == 0;
}
//push
public static void push(int data) {
list.add(data);
}
//pop
public static int pop(){
int top = list.get(list.size()-1);
list.remove(list.size()-1);
return top;
}
// peek
public static int peek() {
return list.get(list.size()-1);
}
}
public static void main(String[] args) {
stack s = new stack();
s.push(1);
s.push(2);
s.push(3);
while(!s.isEmpty()) {
System.out.println(s.peek());
s.pop();
}
}
}