#include <bits/stdc++.h>
using namespace std;
const long double eps = 1e-9;
const int inf = LONG_MAX;
const long long inf64 = LLONG_MAX;
const long double pi = 3.1415926535897932384626433832795;
int a[100100][3];
int dp[100100][2];
int main() {
  int n;
  scanf("%d", &n);
  for (int j = 0; j < 3; j++)
    for (int i = 0; i < n; i++) scanf("%d", &a[i][j]);
  dp[0][0] = 0;
  dp[0][1] = -inf;
  for (int i = 1; i < n; i++) {
    dp[i][0] = max(dp[i - 1][0] + a[i - 1][1], dp[i - 1][1] + a[i - 1][2]);
    dp[i][1] = max(dp[i - 1][0] + a[i - 1][0], dp[i - 1][1] + a[i - 1][1]);
  }
  cout << max(dp[n - 1][0] + a[n - 1][0], dp[n - 1][1] + a[n - 1][1]);
  return 0;
}
