using System;
using System.Threading;

class A {
    public int n = 0;
}

public class TickTack {
    public static void Main() {
        String line;
        Console.WriteLine("Press Enter to terminate...");
        TimerCallback callback = new TimerCallback(PrintTick);
        Timer t = new Timer(callback, new A(), 1000, 1000);
        line = Console.ReadLine();
    }

    static void PrintTick(Object state) {
        int tick = ((A) state).n;
        ((A) state).n = 1 - tick;

        if (tick == 0)
            Console.WriteLine("tick");
        else
            Console.WriteLine("tack");
    }
}