#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int dp[1010][2] = {};
int v;
int main() {
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> v;
		dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
		dp[i][1] = dp[i - 1][0] + v;
	}
	cout << max(dp[n][0], dp[n][1]) << endl;
}