import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int[][] dp=new int[2][n];
    for(int i=0;i<2;i++){
      for(int j=0;j<n;j++){
        dp[i][j]=sc.nextInt();
      }
    }
    for(int i=1;i<n;i++){
      dp[0][i]=dp[0][i-1]+dp[0][i];
    }
    dp[1][0]=dp[0][0]+dp[1][0];
    for(int i=1;i<n;i++){
      dp[1][i]=dp[1][i]+Math.max(dp[0][i],dp[1][i-1]);
    }
    System.out.println(dp[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