#include <bits/stdc++.h>
#define dd(x) cout << #x << "\n"
#define d(x) cout << #x  << ": " << x << "\n"
#define SZ(x) ((int)(x).size())
using namespace std;
#define int long long
using pii = pair<int, int>;
using vpii = vector<pii>;
using vi = vector<int>;
using vii = vector<vector<int>>;
using a3 = array<int, 3>;
using ll = long long;
const int inf = 0x3f3f3f3f3f3f3f3fLL;

// #define MULTI_TEST

void solve() {
    int n; cin >> n;
    vector<int> a(n + 1);
    int gcdv = 0;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
        gcdv = gcd(gcdv, a[i]);
    }

    int ans = gcdv;
    int minx = *min_element(a.begin() + 1, a.end());
    int canMin = 1;
    for(int i = 1; i <= n; i++) {
        if(a[i] == minx) continue;
        if(((a[i] + 1) / 2 + 1) < minx) canMin = false;
    }
    if(canMin) ans = max(ans, minx);

    int globalMin = inf;
    for(int i = 1; i <= n; i++) {
        globalMin = min(globalMin, (a[i] + 1) / 2 + 1);
    }
    ans = max(ans, globalMin);
    cout << ans <<"\n";
}

signed main() {
    ios::sync_with_stdio(false); cin.tie(0);
#ifdef MULTI_TEST
    int T; cin >> T;
#else
    int T = 1;
#endif
    while(T--) solve();
    return 0;
}