#include <bits/stdc++.h>
using namespace std;
int dp[3005][2];
int cst[3][3005];
int main() {
  int n;
  scanf("%d", &n);
  for (int j = 0; j < 3; j++)
    for (int i = 0; i < n; i++) scanf("%d", &cst[j][i]);
  dp[0][0] = -1e8;
  dp[0][1] = 0;
  for (int i = 1; i <= n; i++) {
    dp[i][0] = max(dp[i - 1][0] + cst[1][i - 1], dp[i - 1][1] + cst[0][i - 1]);
    dp[i][1] = max(dp[i - 1][0] + cst[2][i - 1], dp[i - 1][1] + cst[1][i - 1]);
  }
  printf("%d\n", dp[n][0]);
  return 0;
}
