#include <bits/stdc++.h>
using namespace std;
int a[3005], b[3005], c[3005], d[3005], e[3005];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  for (int i = 1; i <= n; i++) cin >> b[i];
  for (int i = 1; i <= n; i++) cin >> c[i];
  d[1] = a[1], e[1] = b[1];
  for (int i = 2; i <= n; i++) {
    d[i] = max(a[i] + e[i - 1], b[i] + d[i - 1]);
    e[i] = max(b[i] + e[i - 1], c[i] + d[i - 1]);
  }
  cout << d[n];
  return 0;
}
