import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N,*W = map(int,read().split())

S = sum(W)

dp = 1
for w in W:
    dp |= dp << w

q,r = divmod(S,2)
if r == 1 or not ((dp>>q)&1):
    print('impossible')
else:
    print('possible')