#include <bits/stdc++.h>
using namespace std;
int r[3010][3];
int dp[3010][2];
int main() {
  int n;
  scanf("%d", &n);
  memset(dp, -1, sizeof(dp));
  dp[0][1] = 0;
  for (int j = 0; j < 3; j++) {
    for (int i = 1; i <= n; i++) scanf("%d", &r[i][j]);
  }
  for (int i = 1; i <= n; i++) {
    if (dp[i - 1][0] != -1) {
      dp[i][0] = max(dp[i][0], r[i][1] + dp[i - 1][0]);
      dp[i][1] = max(dp[i][1], r[i][2] + dp[i - 1][0]);
    }
    if (dp[i - 1][1] != -1) {
      dp[i][0] = max(dp[i][0], r[i][0] + dp[i - 1][1]);
      dp[i][1] = max(dp[i][1], r[i][1] + dp[i - 1][1]);
    }
  }
  printf("%d\n", dp[n][0]);
  return 0;
}
