from itertools import combinations 

def omori(N, W):
    SUM = 0
    for i in range(N):
        SUM += W[i]
    if SUM % 2 != 0:
        return 'impossible'
    half = SUM // 2
    for j in range(1, N//2+1):
        li = list(combinations(W, j))
        for k in range(len(li)):
            sum_k = sum(li[k])
            if sum_k == half:
                return 'possible'
    return 'impossible'
    
    
def main():
    N = int(input())
    W = list(map(int, input().split()))
    print(omori(N, W))
    

if __name__ == '__main__':
    main()