void login(list_users * users){
    int log_tries=3, pas_tries=3;
    list_users * users_start = users;
    string temp_login;
    string temp_password;
    while(logon != 1 && log_tries-- > 0){
        users=users_start;
        system("CLS");
        cout << " Ilosc prob: "<< log_tries+1<<endl;
        cout << " Wprowadz login: ";
        cin >> temp_login;

        while(users){

                if(users->data_users.username == temp_login){

                    while(pas_tries-- > 0){
                        system("CLS");
                        cout << " Ilosc prob: "<< pas_tries+1<<endl;
                        cout << " Wprowadz login: "<< temp_login<<endl;
                        cout << " Wprowadz haslo: ";
                        cin >> temp_password;

                        if(users->data_users.password == temp_password){
                            logon=1;
                            global_user=users->data_users.username;
                            cout << " Zalogowano!\n";
                            system("pause");
                            break;
                        }
                    }
                    break;
                }else
                    users = users->next;
        }

    }
    return;
}