import java.util.ArrayList;
import java.util.Scanner;

public class Kaitenzushi { 

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int N = s.nextInt();
		ArrayList<Integer> V = new ArrayList<>();
		for(int i = 0;i < N;i++){
			V.add(s.nextInt());	
		}
		int MAX;
		s.close();
		if(N == 1){
			MAX = V.get(0);
		}else {
			int Gmax = Integer.max(V.get(0), V.get(1)),NGmax = Integer.min(V.get(0), V.get(1)),count = 0;
			if(N == 2){
			}else{
				for(int i = 2;i < N;i++){
					if(NGmax + V.get(i) > Gmax){
						int n = NGmax;
						NGmax = Gmax;
						Gmax = n + V.get(i);
						count = 0;
					}else{
						if(count == 0){
							count = 1;
						}else{
							int g = Gmax;
							Gmax = NGmax + V.get(i-1);
							NGmax = g;
						}
					}
				}
			}
			MAX = Integer.max(Gmax, NGmax);
		}
		System.out.println(MAX);
	}
}