#include<iostream>
#include<cstring>
#include<vector>
#include<set>
#include<algorithm>
using namespace std;
using LL = long long;

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    int n;
    cin >> n;
    vector<int> a(n);
    for(int i = 0; i < n; i++) cin >> a[i];
    sort(a.begin(), a.end());
    int ans = 0;
    for(int i = n - 1; i >= 0; i--){
        if (a[i] - 1 <= ans){
            cout << ans << '\n';
            return 0;
        }
        vector<int> b;
        for(int j = 0; j < n; j++){
            if (i != j){
                b.push_back(a[j] % a[i]);
            }
        }
        sort(b.begin(), b.end());
        ans = max(ans, (b[n - 3] + b[n - 2]) % a[i]);
        for(int j = 0, k = b.size() - 1; j < b.size(); j++){
            while(k >= 0 and b[j] + b[k] >= a[i]) k--;
            int t = k;
            if (t == j) t--;
            if (t >= 0) ans = max(ans, b[j] + b[t]);
        }
    }
    cout << ans << '\n';

}