#include <bits/stdc++.h>

using namespace std;

class Stack

{

int arr[100010];

int i=0;

public:

void push(int n){arr[i++]=n;}

void pop(){if(i>0)i--;}

void print(){for(int j=0;j<i;j++)cout<<arr[j]<<' ';if(i>0)cout<<endl;}

int size(){return i;}

bool empty(){return i==0;}

int top(){if(i==0)return 1/0;return arr[i-1];}

};

int main()

{

Stack v;

v.push(10);

v.pop();

// cout<<v.top()<<endl;

cout<<v.size()<<endl;

v.print();

v.pop();

cout<<v.size()<<endl;

cout<<v.empty()<<endl;

v.print();

v.push(10);

v.push(20);

v.push(100);

v.push(90);

v.push(101);

v.pop();

v.push(102);

v.print();

cout<<endl;

cout<<v.top()<<endl;

cout<<v.size()<<endl;

}