atc3.cpp

/*
 * VJUDGE C - GCD on Blackboard
 * author: roy4801
 * (C++)
 */
#include <bits/stdc++.h>

using namespace std;

#define PROB "C"
#define TESTC ""

#define USE_CPPIO() ios_base::sync_with_stdio(0); cin.tie(0)
typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<int, int> P;
#define F first
#define S second
#define INF 0x3f3f3f3f
#define MP make_pair
#define MT make_tuple
#define PB push_back
int n, ans;
#define N 1000000
int a[N+5], l[N+5], r[N+5];
int main()
{
	#ifdef DBG
	freopen("./testdata/" PROB TESTC ".in", "r", stdin);
	freopen("./testdata/" PROB ".out", "w", stdout);
	#endif
	while(cin >> n)
	{
		for(int i = 0; i < n && cin >> a[i]; i++);

		l[0] = a[0];
		for(int i = 1; i < n; i++)
			l[i] = __gcd(l[i-1], a[i]);

		r[n-1] = a[n-1];
		for(int i = n-2; i >= 0; i--)
			r[i] = __gcd(r[i+1], a[i]);

		ans = 1;
		for(int i = 1; i < n-1; i++) // [1, n-2]
			ans = max(__gcd(l[i-1], r[i+1]), ans);

		ans = max(max(l[n-2], r[1]), ans);
		printf("%d\n", ans);
	}

	return 0;
}