n = int(input())
w = [int(x) for x in input().split()]
if sum(w)%2 != 0:
    print('impossible')
else:
    hs = sum(w)//2
    m = set([0])
    for i in w:
        nm = set(m)
        for a in m:
            sw = i + a
            if sw == hs:
                print('possible')
                quit()
            nm.add(sw)
        m = nm
    print('impossible')