import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;



public class harry_no_odd_check {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		Map<List<Long>, Integer> map = new HashMap<List<Long>, Integer>();
		long[] avg = {0,0};
		
		int n = sc.nextInt();
		for(int i = 0; i < n; i++)
		{
			List<Long> tuple = new ArrayList<Long>();
			tuple.add(sc.nextLong());
			tuple.add(sc.nextLong());
			avg[0] += tuple.get(0);
			avg[1] += tuple.get(1);
			int count = map.containsKey(tuple) ? map.get(tuple) : 0;
			map.put(tuple, count + 1);
		}
		if(((2 * avg[0]) % n == 0) && ((2 * avg[1]) % n == 0))
		{
			long[] goal = {2 * avg[0] / n, 2 * avg[1] / n};
			Boolean possible = true;
			for (Entry<List<Long>, Integer> entry : map.entrySet())
			{
				List<Long> tuple = entry.getKey();
				List<Long> teammate = new ArrayList<Long>();
				teammate.add(goal[0] - tuple.get(0));
				teammate.add(goal[1] - tuple.get(1));
				if(tuple == teammate) // Probably not necessary.
				{
					if(entry.getValue() % 2 != 0)
						possible = false;
						break;
				}
				else if(!map.containsKey(teammate) || map.get(teammate) != entry.getValue())
				{
					possible = false;
					break;
				}
			}
			if(possible)
			{
				System.out.print("possible");
				return;
			}
		}
		
		System.out.print("impossible");

	}

}