n = int(input())
w = list(map(int, input().split()))
candidate = set([0])
for i in range(n):
    for j in list(candidate):
        candidate.add(w[i] + j)
sumation_w = sum(w)
for i in list(candidate):
    if i*2 == sumation_w:
        print("possible")
        exit()
print("impossible")