#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<int> w(n);
    for (int i = 0; i < n; ++i)
    {
        cin >> w[i];
    }
    int sum = accumulate(w.begin(), w.end(), 0);
    if (sum % 2 == 1)
    {
        cout << "impossible" << endl;
        return 0;
    }
    int lim = sum / 2;
    vector<vector<bool>> cache(lim + 1, vector<bool>(n + 1, false));
    cache[0][0] = true;
    for (int i = 1; i <= lim; ++i)
    {
        for (int j = 1; j <= n; ++j)
        {
            bool result = false;
            for (auto wi : w)
            {
                if (i >= wi)
                {
                    result |= cache[i - wi][j - 1];
                }
            }
            cache[i][j] = result;
        }
    }
    bool result = false;
    for (int i = 1; i <= n; ++i)
    {
        result |= cache[lim][i];
    }
    cout << (result ? "possible" : "impossible") << endl;
    return 0;
}