Problem p03061 (C++)

Buggy submission (status: Runtime Error):
//  Created by conan1024hao on 2019/11/23.
//  Copyright © 2019 conan1024hao. All rights reserved.
//  専用ライブラリです、自由にコピーして構いません。
//  感谢看我的代码！Wechat:conan1024hao QQ:810396815
#pragma GCC optimize("O3")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;
#define INF 10e16
#define MOD 1000000007
#define rep(i, a, n) for (ll i = a; i < (ll)(n); i++)
#define fi first
#define se second
#define mmax(x, y) (x > y ? x : y)
#define mmin(x, y) (x < y ? x : y)
#define chmax(x, y) x = mmax(x, y)
#define chmin(x, y) x = mmin(x, y)
#define all(x) (x).begin(), (x).end()
#define PI acos(-1.0)
long long GCD(long long a, long long b) { return b ? GCD(b, a % b) : a; }
long long LCM(long long a, long long b) { return a / GCD(a, b) * b; }
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
ll cmp(pair<ll, string> a, pair<ll, string> b) {
  if (a.fi != b.fi)
    return a.fi < b.fi;
  else
    return a.se < b.se;
}
//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  //-------------------------------
  int n;
  cin >> n;
  vector<ll> a(n);
  for (ll i = 1; i <= n; i++)
    cin >> a[i];
  vector<ll> l(n + 2);
  vector<ll> r(n + 2);
  vector<ll> m(n + 2);
  sort(all(a));
  l[0] = 0;
  r[n + 1] = 0;
  for (int i = 0; i < n; i++) {
    l[i + 1] = GCD(l[i], a[i]);
  }
  for (int i = n; i > 1; i--) {
    r[i] = GCD(r[i + 1], a[i]);
  }
  for (int i = 1; i <= n; i++) {
    m[i] = GCD(l[i], r[i + 1]);
  }
  ll ans = -1;
  for (int i = 1; i <= n; i++) {
    chmax(ans, m[i]);
  }
  cout << ans << endl;
  //-------------------------------
  return 0;
}
//---------------------------------------------------------------------------


Fixed submission:
//  Created by conan1024hao on 2019/11/23.
//  Copyright © 2019 conan1024hao. All rights reserved.
//  専用ライブラリです、自由にコピーして構いません。
//  感谢看我的代码！Wechat:conan1024hao QQ:810396815
#pragma GCC optimize("O3")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;
#define INF 10e16
#define MOD 1000000007
#define rep(i, a, n) for (ll i = a; i < (ll)(n); i++)
#define fi first
#define se second
#define mmax(x, y) (x > y ? x : y)
#define mmin(x, y) (x < y ? x : y)
#define chmax(x, y) x = mmax(x, y)
#define chmin(x, y) x = mmin(x, y)
#define all(x) (x).begin(), (x).end()
#define PI acos(-1.0)
long long GCD(long long a, long long b) { return b ? GCD(b, a % b) : a; }
long long LCM(long long a, long long b) { return a / GCD(a, b) * b; }
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
ll cmp(pair<ll, string> a, pair<ll, string> b) {
  if (a.fi != b.fi)
    return a.fi < b.fi;
  else
    return a.se < b.se;
}
//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  //-------------------------------
  int n;
  cin >> n;
  vector<ll> a(n + 1);
  for (ll i = 1; i <= n; i++)
    cin >> a[i];
  vector<ll> l(n + 2);
  vector<ll> r(n + 2);
  vector<ll> m(n + 2);
  sort(all(a));
  l[0] = 0;
  r[n + 1] = 0;
  for (int i = 0; i < n; i++) {
    l[i + 1] = GCD(l[i], a[i]);
  }
  for (int i = n; i > 1; i--) {
    r[i] = GCD(r[i + 1], a[i]);
  }
  for (int i = 1; i <= n; i++) {
    m[i] = GCD(l[i], r[i + 1]);
  }
  ll ans = -1;
  for (int i = 1; i <= n; i++) {
    chmax(ans, m[i]);
  }
  cout << ans << endl;
  //-------------------------------
  return 0;
}
//---------------------------------------------------------------------------