#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
template <typename T> inline void read(T &F) {
    int R = 1; F = 0; char CH = getchar();
    for(; !isdigit(CH); CH = getchar()) if(CH == '-') R = -1;
    for(; isdigit(CH); CH = getchar()) F = F * 10 + CH - 48;
    F *= R;
}
inline void file(string str) {
    freopen((str + ".in").c_str(), "r", stdin);
    freopen((str + ".out").c_str(), "w", stdout);
}
const int N = 1e5 + 10;
int ai[N];
int main() {
    //file("");
        int n; read(n);
        for(int i = 1; i <= n; i++) {
            read(ai[i]);
        }
        sort(ai + 1, ai + n + 1);
        if(ai[n] < 0) puts("0");
        else if(ai[n - 1] >= 0) cout << ai[n] + ai[n - 1] << '\n';
        else cout << ai[n] << '\n';
    
    #ifdef _MagicDuck
        fprintf(stderr, "# Time: %.3lf s", (double)clock() / CLOCKS_PER_SEC);
    #endif
    return 0;
}