#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    ios::sync_with_stdio(false);
    int n; cin >> n;
    int a[n], b[n];
    for (int i = 0; i < n; i++) {
        cin >> a[i];

        if (i == 0)
            b[i] = a[i];
        else
        {
            b[i] = a[i] + b[i-1];
        }
        
    }
    
    
    sort(a, a+n);
    for (int i = n-1; i >= 0 ; i--) {
        if (a[i] == b[i-1]) {
            cout << "possible\n";
            return 0;
        }     
    }
    cout << "impossible\n";

    return 0;
}