#include <iostream>
#include <cstdlib>
#include <chrono>   // for class system_clock
#include <ctime>    // for the function localtime
using namespace std;

int main()
{
    const auto now {chrono::system_clock::now()};
    const time_t t {chrono::system_clock::to_time_t(now)};
    const tm *const p {localtime(&t)};

    // Get the current hour of the day (0 to 23 inclusive).
    const int hour {p->tm_hour};

    const int noon {12};
    const int afternoonEnds {17};

    if (hour < noon)
    {
        cout << "Good morning.";
    }
    else if (hour < afternoonEnds)
    {
        cout << "Good afternoon.";
    }
    else
    {
        cout << "Good evening.";
    }

    cout << "\n";
    return EXIT_SUCCESS;
}