import java.util.Arrays;
import java.util.Scanner;

public class Main {

	@SuppressWarnings("resource")
	public static void main(String args[]) {
		Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		int v[]=new int[n];
		for(int i=0;i<n;i++){
			v[i]=scanner.nextInt();
		}
		if(n==1){
			System.out.println(v[0]);
			return;
		}
		int dp[]=new int[n];
		dp[0]=v[0];
		dp[1]=v[1];
		for(int i=0;i<n;i++){
			for(int j=0;j<i-1;j++){
				dp[i]=Math.max(dp[i], dp[j]+v[i]);
			}
		}
		Arrays.sort(dp);
		System.out.println(dp[dp.length-1]);
	}
}