#!/usr/bin/env python3
import sys
input = sys.stdin.readline

n = int(input())
shift = 10**0 + 10
dp = 1 << shift 
w = [int(item) for item in input().split()]
for item in w:
    dp = dp << item | dp >> item
if dp & 1 << shift:
    print("possible")
else:
    print("impossible")