import java.io.*;
import java.util.Arrays;

class Main{
public static void main(String[] args) throws IOException{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String line="";
while((line=br.readLine())!=null){
int n=Integer.parseInt(line);
int[] w=new int[n];
int total=0;
String[] values=br.readLine().split(" ");
for(int i=0;i<n;i++){
w[i]=Integer.parseInt(values[i]);
total+=w[i];
}
Arrays.sort(w);
if(total%2==1){
System.out.println("impossible");
continue;
}
total/=2;
System.out.println(dfs(total,n-1,w)?"possible":"impossible");
}
}
private static boolean dfs(int sum,int now,final int[] w){
if(sum<0||now<0){
return false;
}
if(sum==0){
return true;
}
return dfs(sum,now-1,w)?true:dfs(sum-w[now],now-1,w)?true:false;
}
}