#include <stdio.h>
#include <iostream>
using namespace std;
struct El {
	int data;
	El *next;
};
El *top = NULL;
El *createEl(int x) {
	El *t = new El();
	t->data = x;
	t->next = NULL;
	return t;
}
void push(int x) {
	El *t = createEl(x);
	if (top == NULL) {
		top = t;
		return;
	}
	t->next = top;
	top = t;
}
int pop() {
	if (top == NULL) return 0;
	int res = top->data;
	top = top->next;
	return res;
}
int back() {
	if (top != NULL) return top->data;
}
int size() {
	El *t = top;
	int res = 0;
	while(t != NULL) {
		t->next;
		res++;
	}
	return res;
}
void cleanStack() {
	if(top != NULL) {
		 pop();
		 cleanStack();
	}
}
int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		int x;
		cin >> x;
		push(x);
		cout << "SIZE" << size();
	}
	cout << "size " << size() << " \n";
	cout << "pop " << pop() << "\n";
	cout << "size " << size() << " \n";
	cleanStack();
	cout << "size after  " << size() << " \n";
	return 0;
}