text: #ifndef RESEARCH_HEADER
  #define RESEARCH_HEADER
  #include <iostream>
  using std::string;
  
  enum Research
  {
      InvalidResearchType,
      CheaperBuildings,
      FasterPopulationGrowth
  };
  
  int get_research_cost(Research research);
  
  Research string_to_research(const string &input);
  string research_to_string(const Research research_type);
  
  #endif