n=int(input())
w=list(map(int,input().split()))
w_i=0
for i in w:
    w_i+=i/2
if w_i==int(w_i):
    w_i=int(w_i)
    p=[False]*(w_i+1)
    p[0]=True
    for i in w:
        for k in range(len(p)-1,-1,-1):
            if p[k] and k+i<=w_i:
                p[k+i]=True
    if p[w_i]:
        print("possible")
    else:
        print("impossible")
else:
    print("impossible")