N = int(input())
list1 = list(map(int,input().split()))
a = 0
b = 0
dp = [0]*N
dp[0]=list1[0]
for i in range(N):
    a = a + list1[i]
for i in range(1,N):

    dp[i] = dp[i-1]+list1[i]
    if dp[i]==a/2:
        print("possible")
        b = b+1
        break
if b!=1:
    print("impossible")