Missing constructor for initialization for map

I had some help on a previous topic, where I had to change my map to use int in combination with strings. When I have done this it gives me a different issue. This is the issue:

src/main.cpp:11:29: error: no matching constructor for initialization of
      'std::map<int, std::string>'
  ...tagMap {{"1", "data"}, {"2", "entry"}, {"3", "id"}, {"4", "content"}};
     ^      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It seems like the issue (which I looked up on another topic) seems to allude to the fact that the issue is to do with making your constructor take const references? I don't really understand how to implement this.

#include "pugi/pugixml.hpp"

#include <iostream>
#include <string>
#include <map>

int main()
{
    pugi::xml_document doca, docb;
    std::map<std::string, pugi::xml_node> mapa, mapb;
    std::map<int, std::string> tagMap {{"1", "data"}, {"2", "entry"}, {"3", "id"}, {"4", "content"}};

    if (!doca.load_file("a.xml") || !docb.load_file("b.xml")) {
        std::cout << "Can't find input files";
        return 1;
    }

    for (auto& node: doca.child(tagMap[1]).children(tagMap[2])) {
        const char* id = node.child_value(tagMap[3]);
        mapa[id] = node;
    }

    for (auto& node: docb.child(tagMap[1]).children(tagMap[2])) {
        const char* idcs = node.child_value(tagMap[3]);
        if (!mapa.erase(idcs)) {
            mapb[idcs] = node;
        }
    }
}

Any help would be appreciated.