#include <bits/stdc++.h>
using namespace std;
const int N = 3010;
int dp[N][2], a[N], b[N], c[N];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i < n; i++) cin >> b[i];
  for (int i = 0; i < n; i++) cin >> c[i];
  dp[0][0] = a[0];
  dp[0][1] = 0;
  for (int i = 1; i < n; i++) {
    dp[i][0] = max(dp[i][0], a[i] + dp[i - 1][0] - a[i - 1] + b[i - 1]);
    dp[i][1] = max(dp[i][1], b[i] + dp[i - 1][0]);
    if (i - 1) {
      dp[i][0] = max(dp[i][0], a[i] + dp[i - 1][1] - b[i - 1] + c[i - 1]);
      dp[i][1] = max(dp[i][1], b[i] + dp[i - 1][1]);
    }
  }
  cout << max(dp[n - 1][0], dp[n - 1][1]) << "\n";
}
