N = int(input())
W = list(map(int, input().split()))

goal = sum(W) // 2
if goal * 2 != sum(W):
    print("impossible")
    exit()

dp = [[False for _ in range(sum(W) + 1)] for _ in range(N + 1)]
dp[0][0] = True

for i in range(N):
    for j in range(sum(W) + 1):
        if dp[i][j] == True:
            dp[i + 1][j] = True
            dp[i + 1][j + W[i]] = True

if dp[-1][goal] == True:
    print("possible")
else:
    print("impossible")