n = io.read("*n")
t = {}
t[0] = true
sum = 0
for i = 1, n do
    a = io.read("*n")
    sum = sum + a
    nums = {}
    for k, v in pairs(t) do
        table.insert(nums, k + a)
    end
    for k, v in pairs(nums) do t[v] = true end
end
if(sum % 2 == 0 and t[sum / 2] == true) then print("possible") else print("impossible") end