#coding: UTF-8
import sys

n=input()
w=input()

for num in n:
    total += w[num]
harf = total / 2
if harf % 2 ==1:
    print "impossible"
    sys.exit()
w.sort()
w.reserve()
for num in n:
    if w[num] > harf:
        print "impossible"
        sys.exit()
    elif w[num] == harf:
        print "possible"
        sys.exit()
    else:
        x=n
        break
xharf=w[x]-harf
for i in range(x+1,n):
    flag = w[x]
    if w[i] < xharf:
        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()