#include <iostream>
#include <cmath>
#include <algorithm>

using namespace std;
int main(void) {
	int n;
	cin >> n;
	int buff[2] = { 0 };
	for (int i = 0; i < n; ++i) {
		int sushi;
		cin >> sushi;
		sushi = max(sushi + buff[0], buff[1]);
		buff[0] = buff[1];
		buff[1] = sushi;
	}
	cout << buff[1] << endl;
	return 0;
}