import java.util.*;

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 sum = 0;
        int max = 0;
        int x = 0;
        for(int i=0; i<N; i++){
            for(int j=0; j<N; j++){
                sum += A[x][j];
                if(j==i && x==0){
                    x += 1;
                    j -= 1;
                }
            }
            max = Math.max(max, sum);
            sum = 0;
            x = 0;
        }
        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