n = int(input())
w = list(map(int, input().split()))
dp = [False for i in range(10001)]
dp[0] = True
for i in range(n):
    for j in range(n-1,-1,-1):
        if dp[j] and j + w[i] <= 10000:
            dp[j + w[i]] = True
for i in range(10001):
    if dp[i] and i*2 == sum(w):
        print("possible")
        exit()
print("impossible")