#include <bits/stdc++.h>
using namespace std;
const int N = 3010;
int a[N], b[N], c[N], f[N], g[N], n;
int main() {
  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];
  f[0] = a[0];
  g[0] = b[0];
  for (int i = 1; i < n; i++) {
    f[i] = max(f[i - 1] + b[i], g[i - 1] + a[i]);
    g[i] = max(g[i - 1] + b[i], f[i - 1] + c[i]);
  }
  cout << f[n - 1] << endl;
  return 0;
}
