#include <map>
    #include <set>
    #include <iostream>
    
    using namespace std;
    
    int main() 
    {
    	int row = 0;
    	int col = 0;
        std::map<int, set<int>> sparseBlue;

        // insert empty item
        auto iter = sparseBlue.insert(std::make_pair(row, std::set<int>()));

        // did a new item get inserted?
        cout << "The item did " << (iter.second?"":"not") << " get inserted\n";


        // add item to set 
        (*iter.first).  // the map iterator
               second.  // the set
               insert(col); // what we want to do 
               
       // test
       cout << sparseBlue[row].size() << " item(s) in the set";
    }