n = input()
w = map(int, raw_input().split())
s = sum(w)

dp = [0]*(s+1)
dp[0] = 1
for i in xrange(n):
    for j in xrange(s,w[i]-1,-1):
        dp[j] |= dp[j-w[i]]
print "impossible"*(s%2 or dp[s/2]^1) or "possible"