import java.util.*;
import java.util.stream.*;
import static java.lang.Math.*;
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];
		for(int i=0;i<n;i++){
			dp[i]=v[i];
		}
		for(int i=0;i<n;i++){
			for(int j=i+2;j<n;j++){
				dp[j]=max(dp[j],dp[i]+v[j]);
			}
		}
		put(dp[n-1]);
		
	}
	public static class Pair{
		final int x,y;
		Pair(int x,int y){
			this.x=x;
			this.y=y;
		}
		@Override
		public String toString(){
			return String.format("Pair(%d,%d)",x,y);
		}
	}
	public static void print(Object object){
        System.out.print(object);
    }
    public static void put(Object object) {
        System.out.println(object);
    }
    public static void put(){
        System.out.println();
    }
 
    public static void print(String format,Object... args){
        System.out.print(String.format(format,args));
    }
    public static void put(String format,Object... args) {
        System.out.println(String.format(format,args));
    }
}