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| #include <cstdio>
#include <cmath>
#include <vector>
#include <algorithm>
#include <set>
#include <cstring>
#define LL long long
const int maxn = 1e6 + 5;
using namespace std;
LL a[maxn]; int n;
vector <LL> v;
void split(LL x){
v.clear();
for (LL i = 1; i * i <= x; i++){
if (x % i != 0) continue;
v.push_back(i);
if (i * i != x) v.push_back(x / i);
} sort(v.begin(), v.end());
}
LL _gcd(LL x, LL y){
return (!y) ? x : _gcd(y, x % y);
}
int cnt[10005]; LL ans = 0;
LL max(LL x, LL y){
return x < y ? y : x;
}
int main(){
scanf("%d", &n);
for (int i = 1; i <= n; i++) scanf("%lld", a + i);
for (int T = 0; T < 10; T++){
int u = rand() * rand() % n + 1;
split(a[u]); memset(cnt, 0, sizeof cnt);
for (int i = 1; i <= n; i++){
LL g = _gcd(a[i], a[u]);
vector<LL>::iterator it = lower_bound(v.begin(), v.end(), g);
if (it == v.end()) continue;
cnt[it - v.begin()]++;
}
for (int i = 0; i < v.size(); i++)
for (int j = i + 1; j < v.size(); j++)
if (v[j] % v[i] == 0) cnt[i] += cnt[j];
for (int i = v.size() - 1; i >= 0; i--){
if (cnt[i] >= (n + 1) / 2){
ans = max(ans, v[i]);
break;
}
}
} printf("%lld\n", ans);
return 0;
}
|