import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[][] A = new int[2][N];
        int max = 0;
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < N; j++) {
                A[i][j] = sc.nextInt();
            }
        }
        for (int i = 0; i < N; i++) {
            int count = 0;
            for (int j = 0; j < N; j++) {
                if (j < i) {
                    count += A[0][j];
                } else if (j == i) {
                    count += A[0][j];
                    count += A[1][j];
                } else {
                    count += A[1][j];
                }
            }
            max = Math.max(max, count);
        }
        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