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];
    int[] sum1 = new int[n];
    int[] sum2 = new int[n];
    for(int i = 0; i < 2; i++) {
      for(int j = 0; j < n; j++) {
        a[i][j] = sc.nextInt();
        if(j == 0) {
          if(i == 0) sum1[j] = a[i][j];
          if(i == 1) sum2[j] = a[i][j]; 
        } else {
          if(i == 0) sum1[j] = sum1[j - 1] + a[i][j];
          if(i == 1) sum2[j] = sum2[j - 1] + a[i][j]; 
        }
      }
    }
    int ans = sum1[0] + sum2[n - 1];
    for(int i = 1; i < n; i++) {
      ans = Math.max(ans, sum1[i] + sum2[n - 1] - sum2[i - 1]);
    }
    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