import itertools

n = int(input())
w = [int(x) for x in input().split()]

all_pattern = itertools.combinations_with_replacement("rl",n)

for p in all_pattern:
    right = 0
    left = 0
    possibility = "impossible"
    for i in range(n):
        if p[i] == "r":
            right += w[i]
        else:
            left += w[i]
    if right == left:
        possibility = "possible"
        break

print(possibility)