#include <iostream>
//#include<atcoder/all>
#include <numeric>
#include <cmath>
#include <limits>
#include <stdio.h>
#include <iomanip>
#include <string> 
#include <vector>
#include <algorithm>
#include <utility> 
#include <tuple> 
#include <cstdint> 
#include <cstdio> 
#include <map> 
#include <queue>
#include <set> 
#include <stack> 
#include <deque> 
#include <unordered_map> 
#include <unordered_set>
#include <bitset> 
#include <cctype>
//using namespace atcoder;
using namespace std;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
using Graph = vector<vector<pair<ll, ll>>>;
vector<bool> seen;
bool C = true;
vector<ll> dist;
ll mod =1e9+7;
int op(int a, int b) {
	return min(a, b);
}
int e() {
	return int(1e9);
}

int main() {
	ll N;
	cin >> N;
	vll V(N);
	rep(i, N)cin >> V[i];
	vector<vll> DP(N, vll(2,0));
	DP[0][0] = V[0];
	rep(i, N - 1) {
		DP[i + 1][0] = DP[i][1] + V[i + 1];
		DP[i + 1][1] = max(DP[i][1] ,DP[i][0]);
	}
	cout << max(DP[N - 1][0], DP[N - 1][1]) << endl;
}