#include <bits/stdc++.h>
using namespace std;
int dp[3001][2], n, a[3001], b[3001], c[3001];
int main() {
  int i;
  cin >> n;
  for (i = 1; i <= n; i++) cin >> a[i];
  for (i = 1; i <= n; i++) cin >> b[i];
  for (i = 1; i <= n; i++) cin >> c[i];
  dp[1][0] = a[1];
  dp[1][1] = b[1];
  for (i = 2; i <= n; i++) {
    dp[i][0] = max(dp[i - 1][0] + b[i], dp[i - 1][1] + a[i]);
    dp[i][1] = max(dp[i - 1][0] + c[i], dp[i - 1][1] + b[i]);
  }
  cout << dp[n][0] << endl;
  return 0;
}
