#!/usr/bin/env python3
N = int(input())
W = [int(x) for x in input().split()]
if sum(W) % 2 == 1:
    print("impossible")
    exit()
wanted = sum(W) // 2

if wanted % 2 == 1 and len([0 for w in W if w % 2 == 1]) == 0:
    print("impossible")
    exit()

print("possible")
exit()