#include <bits/stdc++.h>
#include <iostream>
#include<math.h>
using namespace std;
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
int main()
{
    int N;
    cin >> N;
    vector<vector<int>>dp(N+1, vector<int>(2, 0));
    for (int i=0; i<N; i++) {
        int n;
        cin >> n;
        dp[i+1][1] = dp[i][0] + n;
        dp[i+1][0] = max(dp[i][1], dp[i][0]);
    }

    cout << max(dp[N][0], dp[N][1]) << endl;
    return 0;
}