def main():
    """ main """
    N = int(input())
    WS = list(map(int, input().split()))
    total = sum(WS)

    if total & 1 == 1:
        print('impossible')
        return

    half = total >> 1
    dp = set([0])

    for i in WS:
        dp |= set([i+j for j in dp])
        if half in dp:
            print('possible')
            break
    else:
        print('impossible')


main()