package DAY03.P10828;
import jdk.internal.util.xml.impl.Input;
import java.io.*;
import java.nio.Buffer;
import java.util.Arrays;
import java.util.Scanner;
import java.util.Stack;
public class Main {
public static int N;
public static Stack<Integer> stack;
public static void main(String[] args) throws IOException {
System.setIn(new FileInputStream("src/DAY03/P10828/input.txt"));
BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
N = Integer.parseInt(bf.readLine());
stack = new Stack<>();
// bf.readLine();
for (int i=0;i<N;i++){
String command = bf.readLine();
if (command.equals("top")){
if (stack.empty()){
System.out.println(-1);
} else {
System.out.println(stack.peek());
}
} else if (command.equals("size")){
System.out.println(stack.size());
} else if (command.equals("empty")){
boolean result = stack.empty();
if (result){
System.out.println(1);
} else {
System.out.println(0);
}
} else if (command.equals("pop")) {
if (stack.empty()){
System.out.println(-1);
} else {
System.out.println(stack.pop());
}
} else {
// split by " "
String[] command_with_param = command.split(" ");
String command_str = command_with_param[0];
int param = Integer.parseInt(command_with_param[1]);
stack.push(param);
}
}
}
}