n=int(input())
w=[*map(int,input().split())]
s=sum(w)
if s&1:exit(print("impossible"))
m=s>>1
d=[1]+[0]*m
for i in w:
    for j in range(m,i-1,-1):
        d[j]|=d[j-i]
print((""if d[m]else"im")+"possible")