#include <iostream>
#include <map>
#include <limits>
#include <vector>
#include <algorithm>
#include <bitset>
#include <set>
#include <unordered_set>
using namespace std;

using ll = long long;
using ui = unsigned int;

#define int ll

vector<ui> a;

unordered_set<ui> bits;
int diff = 0;

bool check(ui x) {
    ui cnt = __builtin_popcount(a[0] ^ x);
    for (ui y: a) if (__builtin_popcount(y ^ x) != cnt) return false;
    return true;
}

void rec(int i = 0, ui mask = 0, ui cnt = 0) {
    if (cnt > diff) {
        return;
    }
    if (i == 32) {
        if (cnt == diff) {
            if (check(mask)) {if (cnt > diff) {
        return;
    }
                cout << mask << endl;
                exit(0);
            }
        }
        return;
    }
    rec(i + 1, mask, cnt);
    if (bits.count(i)) rec(i + 1, mask | (1 << i), cnt + 1);
}

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int n;
    cin >> n;
    a.resize(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    bitset<32> A(a[0]);
    bitset<32> B(a[0]);
    for (int x: a) {
        if (__builtin_popcount(x) != A.count()) {
            B = x;
            break;
        }
    }
    if (A.count() == B.count()) {
        cout << 0 << endl;
        return 0;
    }
    if (A.count() < B.count()) swap(A, B);
    diff = A.count() - B.count();
    if (diff % 2) {
        cout << -1  << endl;
        return 0;
    }
    diff /= 2;
    cout << A << " " << B << endl;
    for (int i = 0;i < 32; i++) {
        if (A[i] && !B[i]) {
            bits.insert(i);
        }
    }
    rec();
    cout << -1 << endl;
}