#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <iomanip>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
using namespace std;
#define MAX_MOD 1000000007
#define REP(i,n) for(long long i = 0;i < n;++i)
#define LONGINF 1000000000000000000
int main() {
	int n;
	cin >> n;
	int a = 0, b = 0;
	for (int i = 0;i < n;++i) {
		int c;
		cin >> c;
		int d = a;
		a = b + c;
		b = max(d, b);
	}
	cout << max(a, b) << endl;
	return 0;
}