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