# coding: utf-8
import sys
maxW = 100001
N = int(raw_input())
W = map(int, raw_input().split())

#重さの合計が奇数なら終了！
sumW = sum(W)
if sumW % 2 == 1:
    print 'impossible'
    sys.exit()

dp = [[False for _ in range(maxW)] for _ in range(2)]
dp[0][0] = True
c = 0
for weight in W:
    for i in range(maxW):
        if dp[c%2][i]== True:
            dp[(c+1)%2][i] = True
            if i+weight < maxW: dp[(c+1)%2][i+weight] = True
    c+=1

if dp[c%2][sumW/2]:
    print 'possible'
else:
    print 'impossible'