#coding: UTF-8
import sys

n = input()
w = map(int, raw_input().split())
total = 0
for num in range(n):
    total += w[num]
if total % 2 ==1:
    print "impossible"
    sys.exit()
else:
    harf = total / 2
w.sort()
w.reverse()
for num in range(n):
    if w[num] > harf:
        print "impossible"
        sys.exit()
    elif w[num] == harf:
        print "possible"
        sys.exit()
    else:
        x=n
        break
for i in range(x+1,n):
    flag = w[x]
    if w[i] < w[x]-harf:
        flag += w[i]
        for j in range(i-1,n):
            if (flag+w[j]) < harf:
                flag += w[j]
    if flag == harf:
        print "possible"
        sys.exit()
print "impossible"
sys.exit()