void showList(vector<Person> &persons)
{
    showColumns();


    for (auto i = 0; i<persons.size(); ++i)
    {
        cout << left << setw(5) << i+1;
        cout << setw(15) << persons[i].nSignature;
        cout << setw(15) << persons[i].fName + " " + persons[i].lName;
        cout << right << setw(3) << fixed << setprecision(2) << persons[i].length << endl;
        if (i > 0 && (i - 1 % 20 == 0)){
            cout << "Press any key to show the next 20 entries..";
            cin.get();
            rensa();
            showColumns();
        }
    }
    cout << endl;

}