import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[][] arr = new int[2][n];
		for (int i = 0; i < n; i++) {
		    arr[0][i] = sc.nextInt();
		    if (i != 0) {
		        arr[0][i] += arr[0][i - 1];
		    }
		}
		for (int i = 0; i < n; i++) {
		    if (i == 0) {
		        arr[1][i] = sc.nextInt() + arr[0][i];
		    } else {
		        arr[1][i] = Math.max(arr[1][i - 1], arr[0][i]) + sc.nextInt();
		    }
		}
		System.out.println(arr[1][n - 1]);
	}
}

/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