#include <bits/stdc++.h>
using namespace std;
int t[3][3100];
int dp[4][3100];
int n;
int main(void) {
  while (EOF != scanf("%d", &n)) {
    for (int i = 0; i < 3; i++)
      for (int j = 1; j <= n; j++) scanf("%d", &t[i][j]);
    dp[0][1] = t[0][1];
    dp[2][1] = t[1][1];
    dp[1][1] = t[3][1] = 0;
    for (int i = 2; i <= n; i++) {
      dp[0][i] =
          ((dp[2][i - 1]) > (dp[3][i - 1]) ? (dp[2][i - 1]) : (dp[3][i - 1])) +
          t[0][i];
      dp[1][i] =
          ((dp[0][i - 1]) > (dp[1][i - 1]) ? (dp[0][i - 1]) : (dp[1][i - 1])) +
          t[1][i];
      dp[2][i] =
          ((dp[2][i - 1]) > (dp[3][i - 1]) ? (dp[2][i - 1]) : (dp[3][i - 1])) +
          t[1][i];
      dp[3][i] =
          ((dp[0][i - 1]) > (dp[1][i - 1]) ? (dp[0][i - 1]) : (dp[1][i - 1])) +
          t[2][i];
    }
    printf("%d\n", ((dp[0][n]) > (dp[1][n]) ? (dp[0][n]) : (dp[1][n])));
  }
  return 0;
}
