#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < (int)n; ++i)
#define FOR(i, a, b) for(int i = a; i < (int)b; ++i)
#define rrep(i, n) for(int i = ((int)n - 1); i >= 0; --i)

typedef long long ll;
typedef long double ld;

const int Inf = 1e9;
const double EPS = 1e-9;
const int MOD = 1e9 + 7;

int n;
vector<int> w;
bool dfs(int l = 0, int r = 0, int t = 0) {
    bool res = false;
    if (t == n) return l == r;
    res |= dfs(l + w[t], r, t + 1);
    res |= dfs(l, r + w[t], t + 1);

    return res;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(0);
    cin >> n;
    w.resize(n);
    rep (i, n) cin >> w[i];
    if (dfs()) cout << "possible" << endl;
    else cout << "impossible" << endl;
    
    return 0;
}