#include <bits/stdc++.h>
using namespace std;
const int MAXN = 3003;
int N;
int a[MAXN];
int b[MAXN];
int c[MAXN];
int dn[MAXN][2];
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);
  dn[1][0] = a[1];
  dn[1][1] = b[1];
  for (int i = 2; i <= N; i++) {
    dn[i][0] = max(dn[i - 1][1] + a[i], dn[i - 1][0] + b[i]);
    dn[i][1] = max(dn[i - 1][1] + b[i], dn[i - 1][0] + c[i]);
  }
  printf("%d\n", dn[N][0]);
  return 0;
}
