#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[2][n];
  for (int i = 0; i < 2; i++) {
    for (int j = 0; j < n; j++) {
      cin >> a[i][j];
    }
  }
  int max = 0;
  for (int i = 0; i < n; i++) {
    int sum = 0;
    for (int j = 0; j <= i; j++) {
      sum += a[0][j];
    }
    for (int j = i; j < n; j++) {
      sum += a[1][j];
    }
    if (max < sum) max = sum;
  }
  cout << max << endl;
  return 0;
}
