#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <list>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <functional>
using namespace std;
typedef long long int llint;
const int INF = 1000000;
const llint LINF = 100000000;
int main() {
	int n;
	int v[1050];
	for (int i = 0; i < 1050; i++) {
		v[i] = 0;
	}
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> v[i];
	}
	int ans1 = 0, ans2 = 0;
	for (int i = 0; i < 500; i++) {
		ans1 += v[2 * i];
		ans2 += v[2 * i + 1];
	}
	cout << max(ans1, ans2) << endl;
	//cin >> n;
}