#include <bits/stdc++.h>
using namespace std;
long long i, j, k, n, a[100500][3], dp[100500][2];
int main() {
  cin >> n;
  for (j = 0; j < 3; j++)
    for (i = 0; i < n; i++) cin >> a[i][j];
  dp[0][0] = a[0][0];
  dp[0][1] = a[0][1];
  for (i = 1; i <= n; i++) {
    dp[i][0] = max(dp[i - 1][0] + a[i][1], dp[i - 1][1] + a[i][0]);
    dp[i][1] = max(dp[i - 1][0] + a[i][2], dp[i - 1][1] + a[i][1]);
  }
  cout << dp[n - 1][0] << endl;
  return 0;
}
