using System;
using System.Linq;
using System.Collections.Generic;

namespace yukicoder
{
	class pg
	{
		
		static void Main(string[] args)
		{
			int N = int.Parse(Console.ReadLine());
			var weights = Console.ReadLine().Split(' ').Select(c => int.Parse(c)).OrderBy(c => c).ToList();
			
			int total = weights.Sum();
			if(total % 2 == 1)
			{
				Console.WriteLine("impossible");
				return;
			}
			
			int harfTotal = total / 2;
			var explorer = new bool[harfTotal + 1];
			var oldExplorer = new bool[harfTotal + 1];

			for(int i = 0;i < weights.Count;i++)
			{
				if(weights[i] > harfTotal)continue;//配列の範囲外の時
				for(int q = 1;q < harfTotal + 1;q++)
				{
					int pair = q + weights[i];
					if(!oldExplorer[q] || pair > harfTotal)continue;
					
					explorer[pair] = true;
				}
				
				explorer[weights[i]] = true;
				Array.Copy(explorer,oldExplorer,explorer.Length);
			}
			if(explorer[harfTotal])
			{
				Console.WriteLine("possible");
			}else
			{
				Console.WriteLine("impossible");
			}
			
			for(int i = 0;i < explorer.Length;i++)
			{
				Console.WriteLine(i + " " + explorer[i]);
			}
		}
	}
}