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()
S/=2

W.sort()
W.reverse()
A=0
B=0
for w in W:
   if A< B:
      A+=w
   else:
      B+=w
if A==S:
   print "possible"
else:
   print "impossible"