#include <bits/stdc++.h>
using namespace std;
int dp[3005][2], n, a[3005][3];
int solve(int pos = 0, int state = 0) {
  if (pos == n - 1) return a[pos][state];
  int &res = dp[pos][state];
  if (res != -1) return res;
  res = 0;
  if (!state)
    res = max(solve(pos + 1, 1) + a[pos][0], solve(pos + 1, 0) + a[pos][1]);
  else
    res = max(solve(pos + 1, 1) + a[pos][1], solve(pos + 1, 0) + a[pos][2]);
  return res;
}
int main() {
  scanf("%d", &n);
  for (int i = 0; i < 3; ++i)
    for (int j = 0; j < n; ++j) scanf("%d", &a[j][i]);
  memset(dp, -1, sizeof(dp));
  return printf("%d", solve()), 0;
}
