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

struct Record { int id; std::string label; };
struct ById {
    bool operator()(const Record& a, const Record& b) const {
        return a.id < b.id;
    }
};

int main() {
    std::set<Record, ById> records;
    auto first = records.insert(Record{7, "original"});
    auto duplicate = records.insert(Record{7, "replacement"});
    assert(first.second && !duplicate.second);
    assert(duplicate.first->label == "original");

    std::map<int, std::string> names{{10, "ten"}, {30, "thirty"}};
    auto saved = names.find(10);
    names.emplace(20, "twenty");
    assert(saved->second == "ten");
    auto boundary = names.lower_bound(15);
    assert(boundary != names.end() && boundary->first == 20);
    auto missing = names.find(99);
    assert(missing == names.end() && names.size() == 3);
    std::cout << duplicate.first->label << ' ' << boundary->second << '\n';
}