#include <bits/stdc++.h>
using namespace std;
const long long N = 3030;
const long long inf = 1e12;
long long a[N], b[N], c[N], ans[N][4], n;
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n;
  for (long long i = 0; i < (n); ++i) cin >> a[i + 1];
  for (long long i = 0; i < (n); ++i) cin >> b[i + 1];
  for (long long i = 0; i < (n); ++i) cin >> c[i + 1];
  memset(ans, 0, sizeof(ans));
  if (n == 1) {
    cout << a[1];
    return 0;
  }
  ans[1][0] = a[1];
  ans[1][2] = b[1];
  ans[1][1] = ans[1][3] = -inf;
  for (int i = 2; i <= n; i++) {
    ans[i][0] = max(ans[i - 1][2], ans[i - 1][3]) + a[i];
    ans[i][1] = max(ans[i - 1][0], ans[i - 1][1]) + b[i];
    if (i != n) ans[i][2] = max(ans[i - 1][2], ans[i - 1][3]) + b[i];
    if (i != n) ans[i][3] = max(ans[i - 1][0], ans[i - 1][1]) + c[i];
  }
  long long mx = 0;
  for (long long i = 0; i < (4); ++i) mx = max(mx, ans[n][i]);
  cout << mx << endl;
}
