#coding: utf-8
##yuki_4
import sys

def ssum(s,k):
 dp[0]=True
 for i in xrange(len(s)):
  for j in xrange(k,-1,-1):
   if dp[j]==True and j+s[i]<=k:
    dp[j+s[i]]=True
 if dp[k]:
  return True
 return False

n=int(raw_input())
s=map(int,raw_input().split())

sum=0
for i in xrange(len(s)):
 sum+=s[i]

if sum%2==1:
 print "impossible"
 sys.exit()

k=sum/2
dp=[False for i in xrange(n*k+1)]

res=ssum(s,k)
if res==True:
 print "possible"
else:
 print "impossible"