/*
VIM: let b:cf5build="clang -std=c++20 -O2 -pthread -lstdc++ -I. {SRC} -o {OUT}"
VIM: let b:cf5run="{OUT}"
*/
#include <iostream>
#include <exception>
#include <chrono>
#include <unordered_map>
#include <unordered_set>

/*

std::unordered_map<std::string, std::unordered_set<std::string>>
*/

using contacts_type = std::unordered_map<std::string, std::unordered_set<std::string>>;
using emails_type = std::unordered_map<std::string, std::unordered_set<std::string>>;


void
    all_contacts(
    const std::string& contact,
    std::unordered_set<std::string>& visited_contacts,
    const contacts_type& contacts,
    const emails_type& emails,
    std::unordered_set<std::string>& merged_emails)
{
    visited_contacts.insert(contact);
    for (const auto& email: contacts[contact]){
        if (merged_emails.count(email)==0){
            merged_emails.insert(email);
            for (const auto& merging_contacts : emails[email]){
                all_contacts(merging_contacts, visited_contacts, contacts, emails, merged_emails );
            }
        }
    }
}


contacts_type merge( const contacts_type& contacts){

    std::unordered_map<std::string, std::unordered_set<std::string>> emails;

    for (const auto& contact : contacts){
        for (const auto& email : contact.second){
            emails[email].insert(contact.first);
        }
    }

    contacts_type merged_contacts;
    std::unordered_set<std::string> visited_contacts;
    for (const auto& contact : contacts){
        if (visited_contacts.count(contact.first) == 0){
            auto& merged_emails = merged_contacts[contact.first];
            all_contacts(contact.first, visited_contacts, contacts, emails, merged_emails);
        }
    }

    return merged_contacts;
}


int main ( void )
{try{
    auto begin = std::chrono::high_resolution_clock::now();


    //......

    auto end = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> seconds = end - begin;
    std::cout << "Time: " << seconds.count() << std::endl;
    return 0;
}
catch ( const std::exception& e )
{
    std::cerr << std::endl
            << "std::exception(\"" << e.what() << "\")." << std::endl;
    return 2;
}
catch ( ... )
{
    std::cerr  << std::endl
            << "unknown exception." << std::endl;
    return 1;
}}