#include <bits/stdc++.h>
using namespace std;
long long int dp[3005][2], a[3005], b[3005], c[30005];
int main() {
  long long int i, j, k, n, m, x, y;
  cin >> n;
  for (i = 0; i < n; i++) cin >> a[i];
  for (i = 0; i < n; i++) cin >> b[i];
  for (i = 0; i < n; i++) cin >> c[i];
  dp[0][0] = a[0];
  dp[0][1] = b[0];
  for (i = 1; 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 - 1][0];
  return 0;
}
