#include <bits/stdc++.h>
using namespace std;
long long dp[3005][2];
int a[3005], b[3005], c[3005];
int n;
void input() {
  int i;
  scanf("%d", &n);
  for ((i) = (1); (i) <= (n); (i)++) scanf("%d", &a[i]);
  for ((i) = (1); (i) <= (n); (i)++) scanf("%d", &b[i]);
  for ((i) = (1); (i) <= (n); (i)++) scanf("%d", &c[i]);
  dp[1][0] = a[1];
  dp[1][1] = b[1];
  for ((i) = (2); (i) <= (n); (i)++) {
    dp[i][0] =
        ((dp[i - 1][0] + b[i]) > (dp[i - 1][1] + a[i]) ? (dp[i - 1][0] + b[i])
                                                       : (dp[i - 1][1] + a[i]));
    dp[i][1] =
        ((dp[i - 1][0] + c[i]) > (dp[i - 1][1] + b[i]) ? (dp[i - 1][0] + c[i])
                                                       : (dp[i - 1][1] + b[i]));
  }
  printf("%I64d", dp[n][0]);
}
int main() {
  input();
  return 0;
}
