#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define REP1(i, n) for(ll i = 0; i < (n); i++)
#define REP2(i, a, b) for(ll i = (a); i < (b); i++)
#define REP0(n) for(ll iii = 0; iii < (n); iii++)
#define overload3(a, b, c, name, ...) name
#define rep(...) overload3(__VA_ARGS__, REP2, REP1, REP0)(__VA_ARGS__)

#define vl vector<ll>
#define all(v) v.begin(), v.end()
#define fore(e, v) for(auto &&e : v)

template <typename T, typename S> bool chmax(T &x, const S &y) { return (x < y ? x = y, true : false); }

int main() {
    ll n;
    cin >> n;
    vl v(n);
    fore(e, v) cin >> e, chmax(e, 0);

    sort(all(v));
    ll ma = v.end()[-1] + v.end()[-2];

    cout << ma << "\n";
}