n = int(input())
ws = list(input().split())

sum_w = 0

for w in ws:
    sum_w += int(w)


mode_sum_w = sum_w % 2

if mode_sum_w != 0 :
    print('impossible\n')
    exit()

checks = [False] * (sum_w + 1)
checks[0] = True
for w in ws :
    for i in range(sum_w, -1, -1) :
        if not checks[i] :
            continue

        checks[i + int(w)] = True

if checks[sum_w // 2]:
    print("possible\n")
else:
    print("impossible\n")