import java.util.Arrays;
import java.util.Scanner;
import java.util.stream.IntStream;

public class Main {
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[][] field = new int[2][n];
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < n; j++) {
                field[i][j] = sc.nextInt();
            }
        }
        int[] array = new int[n];
        for (int i = 0; i < n; i++) {
            array[i] = IntStream.of(Arrays.copyOfRange(field[0], 0, i + 1)).sum();
            array[i] += IntStream.of(Arrays.copyOfRange(field[1], i, n)).sum();
        }
        System.out.println(Arrays.stream(array).max().getAsInt());
    }
}
/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