UVA - 11850 - Alaska

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Main {
  
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer("");
      
        while(true){
            int n=Integer.parseInt(br.readLine());
            if(n==0)
                break;
            int []arr=new int[n];
            for(int i=0;i<n;i++){
                arr[i]=Integer.parseInt(br.readLine());
            }
            Arrays.sort(arr);
            boolean possible=true;
            if(arr[0]>200){
                possible=false;
            }
            else if(2*(1422-arr[n-1])>200){
                possible=false;
            }
            else{
                for(int i=0;i<arr.length-1;i++){
                    if(arr[i+1]-arr[i]>200){
                        possible=false;
                        break;
                    }
                }
            }
            if(possible){
                sb.append("POSSIBLE").append("\n");
            }else{
                sb.append("IMPOSSIBLE").append("\n");
            }
        }
        System.out.print(sb);
    }
}