#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int n;
int w[100];

bitset<1001> bs[2][101];

int main() {
	cin >> n;
	REP(i, n) scanf("%d", w + i);
	
	bs[0][0][0] = 1;
	REP(i, 100) bs[0][i + 1] |= bs[0][i] << w[i];
	
	bs[1][n][0] = 1;
	for (int i = n - 1; i >= 0; i--) bs[1][i] |= bs[1][i + 1] << w[i];
	
	bool ans = false;
	
	REP(i, n) {
		FOR(j, 1, 1001) if (bs[0][i + 1][j] && bs[1][i + 1][j]) ans = true;
	}
	
	puts(ans ? "possible" : "impossible");
	
	return 0;	
}