如何使set迭代器适应地图迭代器的行为？

#include <set>

struct CustomCompare {
    bool operator()(const std::pair<int, std::string>& lhs, const std::pair<int, std::string>& rhs) const {
        return lhs.first < rhs.first;
    }
};

std::set<std::pair<int, std::string>, CustomCompare> mySet;

std::map<int, std::string> myMap = {{1, "apple"}, {2, "banana"}, {3, "orange"}};

for (const auto& pair : myMap) {
    mySet.insert(pair);
}

for (const auto& pair : mySet) {
    std::cout << pair.first << ": " << pair.second << std::endl;
}