#include <iostream>
#include <cassert>

using namespace std;

class vectorofint
{ protected:
    int * data;
    int capacity;
    int numitems;

  public:
    vectorofint()
    { capacity = 0;
      numitems = 0;
      data = nullptr; }

    ~vectorofint()
    { delete [] data; }

    void resize(int newsize)
    { if (newsize < capacity)
        return;
      int * newdata = new int[newsize];
      for (int i = 0; i < numitems; i += 1)
        newdata[i] = data[i];
      delete [] data;
      data = newdata;
      capacity = newsize; }

    void push_back(int value)
    { if (numitems >= capacity)
      { int newsize = capacity * 2;
        if (newsize <= capacity)
          newsize = capacity + 1;
        resize(newsize); }
      data[numitems] = value;
      numitems += 1; }

    int back()
    { assert(numitems > 0);
      return data[numitems - 1]; }

    void pop_back()
    { assert(numitems > 0);
      numitems -= 1; }

    int at(int position)
    { assert(position >= 0);
      assert(position < numitems);
      return data[position]; }

    void assign(int position, int value)
    { assert(position >= 0);
      assert(position < numitems);
      data[position] = value; }

    int size()
    { return numitems; }
};

int main()
{ vectorofint V;
  V.push_back(123);
  V.push_back(99);
  V.push_back(7);
  V.push_back(12'345'678);
  for (int i = 0; i < V.size(); i += 1)
    cout << V.at(i) << "\n"; }