why the map doesn't work?

[ztdep]

class cellPair
{
  public:
      vector<int> pair;
	  int  size;
	  cellPair(const int& a) {   pair.push_back(a); size=static_cast<int>( pair.size() ); }

   };
 int main()
{
   map<int, cellPair> aMap;
   
  aMap[1]=cellPair(3);
  aMap[1]=cellPair(2);
  
}
  I think the aMap.second.size should ==2, but it still have 1 value, the second value did not push back to the pair.
   Could you please give me some suggestions?

[alwaysLearning0]

every call of cellPair() is creating an object of cellPair, so cellPair(3) and cellPair(2) are two different objects each has one vector in it with 3 and 2 respectively.

aMap[1]=cellPair(3); // first object of cellPair
  aMap[1]=cellPair(2); // second object of cellPair, no relation with the first object