import sys
n = int(input())
a = list(map(int, input().split()))
ans = sum(a)
if ans & 1:
    print("impossible")
    sys.exit()
ans >>= 1

dp = [{} for x in range(n)]

def solve(i, w):
    if w < 0 or i >= n:
        return None
    if w == 0:
        print("possible")
        sys.exit()
        return w
    solve(i + 1, w - a[i])
    solve(i + 1, w)

solve(0, ans)
print("impossible")