include <map>
  include <iostream>
  using namespace std;
  
  class Data
  {
  public:
    Data(int val = 0) { mVal = val; }
    int getVal() const { return mVal; }
    void setVal(int val) {mVal = val; }
    // remainder of definition omitted 
  protected:
    int mVal;
  };
  
  int main(int argc, char** argv)
  {
    map<int, Data> dataMap;
  
    dataMap[1] = Data(4);
    dataMap[1] = Data(6); // replaces the element with key 1
  
    for (map<int, Data>::iterator it = dataMap.begin();
         it != dataMap.end(); ++it) {
      cout << it->second.getVal() << endl;
    }
    return (0);
  }