N=int(input())
l=[0]*(N*100+101)
l[0]=1
s=0
for v in list(map(int,input().split())):
    s+=v
    for i in range(N*100, -1, -1):
        l[i+v]+=l[i]
print("impossible" if s%2==1 or not l[s//2] else "possible")