import java.util.Scanner;

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;
		int right = 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++) {
			right += a[0][i];
			int sum = right;
			for(int j = i; j <n; j++) {
				sum += a[1][j];
			}
			max = Math.max(sum, 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