#include <bits/stdc++.h>
using namespace std;
int n, a[3005], b[3005], c[3005];
int f[3005], g[3005];
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
  for (int i = 1; i <= n; ++i) scanf("%d", &b[i]);
  for (int i = 1; i <= n; ++i) scanf("%d", &c[i]);
  f[1] = a[1];
  g[1] = b[1];
  for (int i = 2; i <= n; ++i) {
    f[i] = max(f[i - 1] + b[i], g[i - 1] + a[i]);
    g[i] = max(f[i - 1] + c[i], g[i - 1] + b[i]);
  }
  printf("%d\n", f[n]);
  return 0;
}
