#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define srep(i, s, n) for (int i=(s); i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define fore(i,x) for(auto i:x)
#define pb push_back

using vi=vector<int>;
using vvi=vector<vi>;
using vb=vector<bool>;
using vvb=vector<vb>;
using vs=vector<string>;
using vll=vector<long long>;
using vvll=vector<vll>;
using vc=vector<char>;
using vvc=vector<vc>;
using ll=long long;

void Yes(bool ok){ cout << (ok ? "Yes" : "No") << "\n";}

int main(){
    int N; cin >> N;
    vi V(N);
    rep(i,N) cin >> V.at(i);
    vvi dp(N+1,vi(2));
    rep(i,N){
        dp.at(i+1).at(0)=max(dp.at(i+1).at(0),dp.at(i).at(1)+V.at(i));
        dp.at(i+1).at(1)=max(dp.at(i+1).at(1),max(dp.at(i).at(1),dp.at(i).at(0)));
    }
    int ans=max(dp.at(N).at(0),dp.at(N).at(1));
    cout << ans << "\n";
}