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];
		for(int i = 0; i < N; i++) {
			A[0][i] = sc.nextInt();
		}
		for(int i = 0; i < N; i++) {
			A[1][i] = sc.nextInt();
		}
		sc.close();
		if(N == 1) {
			System.out.println(A[0][0] + A[1][0]);
			System.exit(0);
		}
		int[][]B = new int[2][N];
		B[0][0] = A[0][0];
		B[1][0] = A[1][0] + A[0][0];
		for(int i = 1; i < N; i++) {
			B[0][i] = B[0][i - 1] + A[0][i];
			B[1][i] = B[1][i - 1] + A[1][i];
		}
		for(int i = 1; i < N; i++) {
			B[1][i] = Math.max(B[1][i - 1], B[0][i]) + A[1][i];
		}
		System.out.println(B[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