N = int(input())
W = list(map(int, input().split()))
W_sum = sum(W)
from itertools import combinations
# from collections import defaultdict
# d = defaultdict(int)
for i in range(1, N+1):
    for j in combinations(W, i):
        j_sum = sum(j)
        if j_sum == W_sum-j_sum:
            print("possible")
            exit()

        
print("impossible")