//sidcodes

#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

typedef priority_queue<int, vector<int>, greater<int>> pqmin;

#define endl '\n'

#define pb push_back

#define all(x) (x).begin(), (x).end()

#define rall(x) (x).rbegin(), (x).rend()

#define fi first

#define se second

#define fr(i,n) for(int i=0;i<n;i++)

#define pyes cout<<"YES\n"

#define pno cout<<"NO\n"

typedef pair<int,int> pii;

typedef pair<ll,ll> pll;

typedef vector<int> vi;

typedef vector<ll> vll;

typedef vector<pll> vpll;

typedef vector<pii> vpii;

typedef vector<vll> vvll;

const int MOD = 1e9+7;

#ifndef ONLINE_JUDGE

#define debug(x) cerr << #x << " = "; _print(x); cerr << endl;

#else

#define debug(x)

#endif

void _print(int t) {cerr << t;}

void _print(string t) {cerr << t;}

void _print(char t) {cerr << t;}

void _print(long double t) {cerr << t;}

void _print(double t) {cerr << t;}

void _print(unsigned long long t) {cerr << t;}

void _print(long long t) {cerr << t;}

template <class T, class V> void _print(pair<T, V> p);

template <class T> void _print(vector<T> v);

template <class T> void _print(set<T> v);

template <class T, class V> void _print(map<T, V> v);

template <class T> void _print(multiset<T> v);

template <class T, class V> void _print(pair<T, V> p) {cerr << "{"; _print(p.first); cerr << ","; _print(p.second); cerr << "}";}

template <class T> void _print(vector<T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}

template <class T> void _print(set<T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}

template <class T> void _print(multiset<T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}

template <class T, class V> void _print(map<T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}

ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }

ll lcm(ll a, ll b) { return (a / gcd(a, b)) * b; }

vector<ll> fact, invfact;

ll modpow(ll a, ll b, ll mod = MOD) {

ll res = 1;

while (b) {

if (b & 1) res = (res * a) % mod;

a = (a * a) % mod;

b >>= 1;

}

return res;

}

void init_nck(int maxn){

fact.assign(maxn+1, 1);

invfact.assign(maxn+1, 1);

for(int i = 1; i <= maxn; i++)

fact[i] = (fact[i-1] * i) % MOD;

invfact[maxn] = modpow(fact[maxn], MOD - 2);

for(int i = maxn-1; i >= 0; i--)

invfact[i] = (invfact[i+1] * (i+1)) % MOD;

}

ll nck(ll n, ll r){

if(r < 0 || r > n) return 0;

return (((fact[n] * invfact[r]) % MOD) * invfact[n-r]) % MOD;

}

vector<vll> adj;

vll depth, parent, sub;

vector<vll> dp;

void dfs(ll u, ll p) {

parent[u] = p;

sub[u] = 1;

for (auto v : adj[u]) {

if (v == p) continue;

depth[v] = depth[u] + 1;

dfs(v, u);

sub[u] += sub[v];

}

}

void solve() {

ll n;

cin>>n;

vll v(n);

fr(i,n) cin>>v[i];

set<ll>s(all(v));

if(s.size()==1){

cout<<v[0];

return;

}

sort(all(v));

set<ll> ans;

// c1 L not in arr

if(n%2==0){

set<ll> temp;

ll i=0;

ll j=n-1;

while(i<j){

temp.insert(v[i]+v[j]);

i++;

j--;

}

if(temp.size()==1){

ans.insert(v[0]+v[n-1]);

}

}

// in arr

ll i=0;

ll j=n-1;

ll mx=v[n-1];

bool poss=1;

while(i<j){

if(v[j]==mx){

j--;

continue;

}

else if(v[i]+v[j]!=mx){

poss=0;

break;

}

i++;

j--;

}

if(poss) ans.insert(mx);

for(auto i:ans) cout<<i<<" ";

}

int main() {

ios::sync_with_stdio(0);

cin.tie(0);

int t = 1;

// cin >> t;

while (t--) {

solve();

}

return 0;

}