C++ :

#define Max(a,b)((a)>(b)?(a):(b))

#include<cstdio>

using namespace std;

bool v[1000005];
int n,a[10005],Maxn,ans;
int tot,k,cnt,b,c;

int gcd(int a,int b)
{
	if(b==0)return a;
	return gcd(b,a%b);
}

void work1()
{
	for(int i=1;i<=n;i++){
		if(a[i]<=ans)continue;
		for(int j=i+1;j<=n;j++){
			if(a[j]<=ans)continue;
			k=gcd(a[i],a[j]);
			if(k>ans){
				b=a[i];c=a[j];
				ans=k;
			}
		}
	}printf("%d",ans);
}

void work2()
{
	for(int i=Maxn;i>=1;i--){
		cnt=0;
		for(int j=1;i*j<=Maxn;j++)
		    if(v[i*j]==1)
			{
				cnt++;
				if(cnt>=2){
					printf("%d",i);
					return;
				}
		    }
	}
}

int main()
{
	scanf("%d",&n);ans=1;Maxn=0;
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
		v[a[i]]=1;Maxn=Max(Maxn,a[i]);
 	}
	work2();
}