c++ map

#include <iostream>
#include <map>
using namespace std;
int main()
{
   map<int, int> edges;
    bool a;
   edges.insert(pair<int, int>(000, 100));
    a=edges.insert(pair<int, int>(002, 300)).second;
    std::cout<<a<<endl;
   a=edges.insert(pair<int, int>(002, 345)).second;
    std::cout<<a<<endl;
   if(a==false)// insert fail, updata, erase, then insert
   {
      edges.erase(002); 
        a=edges.insert(pair<int, int>(002, 345)).second;
        std::cout<<a<<endl;
   }
   
   map<int, int>::iterator v = edges.begin();
   while (v != edges.end())
   {
      cout << v->first << "," << v->second << endl;
      v++;
   }
   return 0;
}