#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:16777216")
using namespace std;
int DP[4000][4], n, a[4000], b[4000], c[4000];
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);
  DP[1][0] = a[1];
  DP[1][1] = a[1];
  DP[2][0] = a[1] + b[2];
  DP[2][1] = a[2] + b[1];
  for (int i = 3; i <= n; i++) {
    DP[i][0] =
        (DP[i - 1][0] > DP[i - 1][1] ? DP[i - 1][0] : DP[i - 1][1]) + b[i];
    DP[i][1] = a[i] + DP[i - 1][0] + c[i - 1] - b[i - 1];
    DP[i][1] = (DP[i][1] > a[i] + DP[i - 1][1] + b[i - 1] - a[i - 1]
                    ? DP[i][1]
                    : a[i] + DP[i - 1][1] + b[i - 1] - a[i - 1]);
  }
  printf("%d\n", (DP[n][0] > DP[n][1] ? DP[n][0] : DP[n][1]));
}
