#include<iostream>
#include<vector>
#include<bitset>
#include<algorithm>
#include<cmath>
#include<string>
#include<queue>
#include<numeric>//iota -- iota(all(a), x) a从头到尾从x开始递增
#include<cstring>
#include<ctime>
#include<array>
#include<list> 
#include<random>
#include<tuple>
#include<deque>
#include<map>
#include<stack>
#include<set>
using namespace std;
#define IOS ios::sync_with_stdio(false);cin.tie(0), cout.tie(0)
#define int long long
#define all(x) x.begin(), x.end()
#define pb push_back
#define pf push_front
#define lowbit(x) (x & (-x))
const int xy[][2] = { 0,1, 0, -1, 1, 0, -1, 0 };
#define mem(a, x) memset(a, x, sizeof a)
typedef long long ll;
typedef pair<int, int> PII;
typedef pair<double, double> PDD;
typedef pair<char, char> PCC;
typedef pair<int, char> PIC;
typedef pair<char, int> PCI;
#define x first
#define y second
#define NO cout << "NO\n"
#define YES cout << "YES\n"
inline int read();
const int INF = 1e9, N = 1e4 + 10, MOD = 998244353, M = 1e4 + 10, K = 1331;
const double PI = acos(-1.0);
void solve() {
    int n; cin >> n;
    priority_queue<int, vector<int>, less<int>>q;
    int ret(0);
    for (int i = 1; i <= n; i++) {
        int x; cin >> x;
        if (q.size())ret = max(ret, x + q.top());
        q.push(x);
    }
    cout << ret << endl;
}
signed main() {
    IOS;
    int _ = 1;
    //cin >> _;
    while (_--)solve();
    return 0;
}
inline int read()
{
    int x = 0, f = 1; char ch = getchar();
    while (ch < '0' || ch>'9') { if (ch == '-') f = -1; ch = getchar(); }
    while (ch >= '0' && ch <= '9') { x = x * 10 + ch - 48; ch = getchar(); }
    return x * f;
}
/*   /\_/\
*   (= ._.)
*   / >  \>
*/