import math

N = int(raw_input())
W = map(int, raw_input().split())
S=0
for w in W:
   S+=w
if S%2 != 0:
   print "impossible"
   exit()

W.sort()
L = [False for i in range(S+1)]
L[0]=True
for w in W:
   for i in range(S,-1,-1):
      if L[i] and i+w <=S:
         L[i+w]=True
if L[S/2]:
   print "possible"
else:
   print "impossible"