import java.util.Scanner;

class Main{
	public static void main(String args[]){
		Scanner sc=new Scanner(System.in);
		int N = sc.nextInt();
		int[][] A = new int[2][N];
		for(int i = 0; i < 2; i++) {
			for(int j = 0; j < N; j++) A[i][j] = sc.nextInt();
		}
		int[] upper_sum = new int[N];
		int[] lower_sum = new int[N];
		for(int i = 0; i < N; i++) {
			upper_sum[i] = (i == 0) ? A[0][i] : upper_sum[i - 1] + A[0][i];
		}
		for(int i = N - 1; i >= 0; i--) {
			lower_sum[i] = (i == N - 1) ? A[1][i] : lower_sum[i + 1] + A[1][i];
		}
		int ans = 0;
		for(int i = 0; i < N; i++) {
			ans = Math.max(ans, upper_sum[i] + lower_sum[i]);
		}
		System.out.println(ans);
	}
}
/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