#include <bits/stdc++.h>
using namespace std;
constexpr long long ROWS = 2;
constexpr long long NMAX = 1e5;
long long h[ROWS][NMAX];
long long dp[ROWS][NMAX];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long COLS;
  cin >> COLS;
  for (long long i = 0; i < ROWS; ++i)
    for (long long j = 0; j < COLS; ++j) cin >> h[i][j];
  for (long long j = COLS - 1; j >= 0; --j)
    for (long long i = ROWS - 1; i >= 0; --i) {
      if (j == COLS - 1)
        dp[i][j] = h[i][j];
      else if (j == COLS - 2)
        dp[i][j] = h[i][j] + h[i == 0 ? 1 : 0][j + 1];
      else
        dp[i][j] =
            h[i][j] + max(dp[i == 0 ? 1 : 0][j + 1], dp[i == 0 ? 1 : 0][j + 2]);
    }
  cout << max(dp[0][0], dp[1][0]);
  return 0;
}
