import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int [] V = new int [N];
        for(int i=0; i<N; i++){
            V[i]=sc.nextInt();
        }
        int [] dp = new int [N];
        dp[0]=V[0];
        dp[1]=V[1];
        for(int i=2; i<N; i++){
            dp[i]=Math.max(dp[i-1],dp[i-2]+V[i]);
        }
        System.out.println(Math.max(dp[N-1],dp[N-2]));
    }
}