E: 2vec

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

#define int long long

int gsd(int a, int b) {
    return (b == 0 ? a : gsd(b, a % b));
}

int main() {
    int n, k, news;
    cin >> n >> k;
    vector<int> vec(n);
    for (int i = 0; i < n; i++) cin >> vec[i];
    for (int i = 0; i < k - (n % k); i++) vec.push_back(0);
    vector<int> l(1, 0), r(1, 0);

    for (int j = k - 1; j >= 0; j--)
        l.push_back(gsd(max(l.back(), vec[j]), min(l.back(), vec[j])));
    int maxx = l.back();

    for (int i = k; i < vec.size(); i++) {

        if (l.size() == 1) {
            r.clear(); r.push_back(0);
            for (int j = i - 1; j >= i - k; j--)
                l.push_back(gsd(max(l.back(), vec[j]), min(l.back(), vec[j])));
        }

        l.pop_back();
        r.push_back(gsd(max(r.back(), vec[i]), min(r.back(), vec[i])));
        maxx = max(maxx, gsd(max(r.back(), l.back()), min(r.back(), l.back())));
    }

    cout << maxx;
    return 0;
}