#include<bits/stdc++.h>
#define F first
#define S second
#define MP make_pair
#define pb push_back
#define endl '\n'

using namespace std;

typedef long long LL;
typedef pair< int, int > P;
typedef pair< LL, LL > LP;
typedef pair< int, P > iP;
typedef pair< P, P > PP;

static const int INF = INT_MAX;
static const LL LINF = LLONG_MAX;
static const int MIN = INT_MIN;
static const LL LMIN = LLONG_MIN;
static const int MOD = 1000000007;
static const int SIZE = 100005;

int dx[] = {0, -1, 1, 0};
int dy[] = {-1, 0, 0, 1};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    string ch;
    cin >> n;
    LL a[3];
    string s;
    cin >> ch;
    getline( cin, s );
    
    if( s.find( ' ' ) != -1 ) {
        cout << "\"assert\"" << endl;
        return 0;

    }
    a[0] = 0;
    LL dig = 1;
    int pos = ch.size() - 1;
    while( pos >= 0 ) {
        a[0] += ( ch[pos] - '0' ) * dig;
        --pos;
        dig *= 10;

    }
    for( int i = 1; i < n; ++i ) cin >> a[i];
    priority_queue< LL > res;
    set< LL > st;
    
    for( int i = 0; i < n - 1; ++i ) {
        for( int j = i + 1; j < n; ++j ) {
            int p = st.size();
            st.insert( a[i] + a[j] );
            if( p != st.size() ) {
                res.push( a[i] + a[j] );

            }

        }
    }
    
    if( res.size() != 1 ) {
        res.pop();

    }
    cout << res.top() << endl;

    return 0;
}