#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline T abs(T a) {
  return a < 0 ? (-a) : a;
}
template <typename T>
inline T sqr(T x) {
  return x * x;
}
int main() {
  int n;
  cin >> n;
  vector<int> a(n), b(n), c(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];
  }
  if (n == 1) {
    cout << a[0] << endl;
    return 0;
  }
  long long res1 = a[0] + b[1];
  long long res0 = b[0] + a[1];
  for (int i = 2; i < n; ++i) {
    long long nres1 = b[i] + max(res0, res1);
    long long nres0 =
        a[i] + max(res0 - a[i - 1] + b[i - 1], res1 - b[i - 1] + c[i - 1]);
    res0 = nres0;
    res1 = nres1;
  }
  cout << max(res0, res1) << endl;
  return 0;
}
