import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner scan = new Scanner(System.in)) {
            
            int n = scan.nextInt();
            int list[] = new int[n];
            int dp[] = new int[n];
            
            for(int i=0; i<n; i++) {
                list[i] = scan.nextInt();
                dp[i] = list[i];
            }
            
            if(n == 1) {
                System.out.println(list[0]);
            } else if(n == 2){
                if(list[0] > list[1]) System.out.println(list[0]);
                else                  System.out.println(list[1]);
            } else {
                for(int i=2; i<n; i++) {
                    for(int j=0; j<=i-2; j++) {
                        if(dp[j] + list[i] > dp[i]) dp[i] = dp[j] + list[i];
                    }
                }
                int ans = 0;
                for(int i=0; i<n; i++) {
                    ans = Math.max(ans, dp[i]);
                }
                System.out.println(ans);
            }
        }
    }
}