import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Deque;
import java.util.Scanner;

public class OmoritoTenbin {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int N = s.nextInt(),rest = 0;
		int[] W = new int[N];
		for(int i = 0;i < N ;i++){
			W[i] = s.nextInt();
			rest += W[i];
		}
		s.close();
		Arrays.sort(W);
		int kw = 0;
		ArrayList<Integer> list = new ArrayList<>();
		if(rest%2 == 1){
			System.out.println("impossible");
		}else{
			rest /=2;
			Deque<Integer> stack = new ArrayDeque<>();
			for(int i :W){
				stack.push(i);
				list.add(i);
			}
			while(stack.size() != 0){
				int w = stack.pop();
				//System.out.println(stack);
				if(rest-w == 0){
					System.out.println("possible");
					break;
				}else if(rest-w > 0 && rest-w-list.get(0) >= 0){
					for(int i = 0;i < list.indexOf(w);i++){
						stack.push(list.get(i));
					}
					rest -= w;
					kw = w;
					//System.out.println(rest + "  " + w);
				}else if(w == list.get(0) && rest - w != 0){
					rest += kw;
				}
				if(stack.size() == 0){
					System.out.println("impossible");
				}
			}
		}
	}
}