n = int(raw_input())
l = map(int, raw_input().split())
ls = [False for _ in range(100*n+1)]
ls[0] = True
for w in l:
    for i in range(100*n,-1,-1):
        if ls[i]:
            ls[i+w] = True
if sum(l) % 2 == 1 or ls[sum(l)/2] == False:
    print 'impossible'
else:
    print 'possible'