count_to(5);

void count_to(int max) {
    for (int i = 0; i < max; i++) {
        Console.Write($"{i}, ");
    }
}

int[] schedule = {800, 1200, 1600, 2000};

void display_adjusted_times(int[] times, int current_GMT, int new_GMT) {
    int diff = 0;
    if (Math.Abs(new_GMT) > 12 || Math.Abs(current_GMT) > 12){
        Console.WriteLine("Invalid GMT");
    } else if (
            new_GMT <= 0 && current_GMT <= 0 ||
            new_GMT >= 0 && current_GMT >= 0
        ){
        diff = 100 * (Math.Abs(new_GMT) - Math.Abs(current_GMT));
    } else {
        diff = 100 * (Math.Abs(new_GMT) + Math.Abs(current_GMT));
    }
    for (int i=0; i<times.Length; i++){
        int new_time = ((times[i] + diff)) % 2400;
        Console.WriteLine($"{times[i]} -> {new_time}");
    }
}

display_adjusted_times(schedule, 6, -6);