# -*- coding: utf-8 -*-
#input
N = input()
W = map(int, raw_input().split())
if sum(W) % 2 == 1:
    print "impossible"
    exit()
sumhalf = sum(W) / 2

# dynamic programming
DP = [0] * (sumhalf + 100)
DP[0] = 1
for w in W:
    for i in reversed(range(sumhalf)):
        if DP[i] == 1:
            DP[i + w] = 1

# output
if DP[sumhalf] == 1:
    print "possible"
else:
    print "impossible"