how to insert data in a map where the key is picked from a std::set and value from a map of structures

The code snippet below apparently tries to create three types of maps. The below code works really fine without the line commented out (This is the final hash that i would like to create). I would like to insert data into the final map myData , and when i uncomment the line below code doesnt work

data1.insert( std::make_pair( e_group[1]["ET"], m_wayside1) )

How to access the specific value in a set of a specific key

#include <map>
#include <iostream>
#include <string>
#include <vector>
#include <set>



struct values
{
    std::string a;
    std::string b;
    values():a("milepost"),b("dummyval"){};
    values( std::string ab, std::string bc)
    {
        a=ab;
        b=bc;

    };
};



typedef  std::map<std::string,values> my_waysides ;
typedef  std::map <int, std::set<std::string> > groups;
typedef  std::map <groups,my_waysides> myData;

int main(int argc, const char * argv[]) {

    my_waysides  m_wayside1,m_wayside2,m_wayside3;
    groups  e_group,e_group1,e_group2;
    values b,c,d;
    std::set<std::string> myGroups;
    myData data1;

    myGroups.insert("ET");
    myGroups.insert("PT");

    e_group.insert( std::make_pair(1,myGroups) );
    e_group.insert( std::make_pair(2,myGroups) );
    e_group.insert( std::make_pair(3,myGroups) );
    m_wayside1.insert(std::make_pair("7802543",b));

 //   data1.insert( std::make_pair( e_group[1]["ET"], m_wayside1) )

    for (auto &i : e_group){
        std::cout<<i.first<<"\t";
        for (std::set<std::string> :: const_iterator it = i.second.begin() ; it != i.second.end() ; it++ )
        {
            std::cout<<*it<<"\t";

        }
        std::cout<<"\n";

    }
    std::cout << "Hello, World!\n";
    return 0;
}