#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <utility>
#include <functional>
#include <sstream>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>
#include <fstream>
using namespace std;
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<class T> inline string toStr(T x) { ostringstream sout; sout << x; return sout.str(); }
typedef vector<int> vi;
typedef vector<vi>  vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define REP(i,n) FOR(i,0,(n)-1)
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = INT_MAX / 10;

int main() {
	int N;
	cin >> N;
	vi W(N+1);
	int S = 0;
	FOR(i, 1, N) {
		cin >> W[i];
		S += W[i];
	}

	if (S % 2) {
		cout << "impossible" << endl;
		return 0;
	}

	vvi dp(N + 1, vi(S + 1, 0));
	dp[0][0] = 1;
	int M = 0;
	FOR(i, 1, N) {
		dp[i][0] = 1;
		FOR(j, 0, M) {
			dp[i][j] += dp[i - 1][j];
			dp[i][j + W[i]] += dp[i - 1][j];
		}
		M += W[i];
	}

	if (dp[N][S / 2]) {
		cout << "possible" << endl;
	}
	else {
		cout << "impossible" << endl;
	}

	return 0;
}