N = int(input())
W = list(map(int,input().split()))
sum = 0
for i in range(N):
    sum += W[i]
dp = [[0 for _ in range(sum+1)] for _ in range(N)]
dp[0][0] = 1
if sum % 2 == 1:
    print("impossible")
    exit()

dp[0][W[0]] = 1

for i in range(1,N):
    for j in range(sum+1):
        if dp[i-1][j] == 0:
            continue
        dp[i][j] = 1
        dp[i][j+W[i]] = 1

if dp[N-1][sum//2] == 1:
    print("possible")
else:
    print("impossible")