import java.util.*;
class Main
{
    public static void main (String[] args)
    {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        int[] b = new int[n];
        a[0] = sc.nextInt();
        for(int i = 1; i < n; i++) a[i] = a[i-1] + sc.nextInt();
        b[0] = sc.nextInt();
        for(int i = 1; i < n; i++) b[i] = b[i-1] + sc.nextInt();
        int ans = a[0] + b[n-1];
        for(int i = 1; i < n; i++)
            ans = Math.max(ans, a[i] + b[n-1] - b[i-1]);
        System.out.println(ans);
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz