#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

int main() {

    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    int n;
    cin >> n;
    vector<int> vec(n);
    int sum = 0;
    for (auto& i : vec) {
        cin >> i;
        sum += i;
    }

    sort(vec.begin(), vec.end(), greater<int>());
    if (sum % 2 == 1 || vec.at(0) > sum / 2) {
        cout << "impossible" << endl;
        return 0;
    }
    bool flag = false; //possibleならtrue
    vector<int> y(sum + 1, 0);
    y.at(0) = 1; //check済
    stack<int> s;
    auto itr = vec.begin();
    int weight = 0;
    while (true) {
        s.push(*itr);
        weight += s.top();
        s.pop();
        if (y.at(weight) == 0) {
            if (weight == sum / 2) {
                flag = true;
                break;
            } else if (weight < sum / 2) {
                y.at(weight) = 1; //check済
                ++itr;
            } else {
                y.at(weight) = 1; //check済
                weight -= static_cast<int>(*itr);
                ++itr;
            }
        }
        if (itr == vec.end()) break;
    }
    cout << ((flag) ? "possible" : "impossible") << endl;
    return 0;
}
// 3 2 1 , sum=6 
// 5 4 3 2 , sum=14
// 2 3 5 9 10 11 12 sum=52