import java.io.BufferedReader;
import java.io.InputStreamReader;


public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        String str_raw1[] = br.readLine().split(" ");
        String str_raw2[] = br.readLine().split(" ");
        int[] raw1 = new int[n];
        int[] raw2 = new int[n];
        for (int i = 0; i < n; i++) {
            raw1[i] = Integer.parseInt(str_raw1[i]);
            raw2[i] = Integer.parseInt(str_raw2[i]);
        }
        
        int[] sums = new int[n];
        int max = -1;
        for (int i = 0; i < n; i++) {
            sums[i] = 0;
            for (int j = 0; j <= i; j++) {
                sums[i] += raw1[j];
            }
            for (int k = i; k < n; k++) {
                sums[i] += raw2[k];
            }
            max = Math.max(sums[i], max);
        }
        
        System.out.println(max);
    }
}

/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