import java.util.Scanner;

public class Main45 {
	public static void main(String[] args) {
		Main45 p = new Main45();
	}

	public Main45() {
		Scanner sc = new Scanner(System.in);
		int n= sc.nextInt();
		int[] v = new int[n];
		for (int i = 0; i < v.length; i++) 
			v[i] = sc.nextInt();
	
		solve(v);
	}

	public void solve(int[] v) {
		int[] sum =new int[2];
		int cur = 0;
		
		for(int i=0;i<v.length;i++){
			sum[cur] = Math.max(sum[cur]+v[i], sum[1-cur]);
			cur = 1 - cur;
		}
		
	
		System.out.println(sum[1-cur]);
	}

}