import java.util.Arrays;
import java.util.Scanner;
public class No4 {
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int[] w=new int[sc.nextInt()];
		int l=0,r=0;
		for(int i=0;i<w.length;i++)w[i]=sc.nextInt();
		Arrays.sort(w);
		for(int i=w.length-1;i>=0;i--)
		if(l<r)l+=w[i];
		else r+=w[i];
		System.out.println(l==r?"possible":"impossible");
	}
}