#include <bits/stdc++.h>
using namespace std;
int DEBUGGING = 0;
const int INF = 1000000000;
const int MOD = 1000000007;
const double PI = 3.1415926535897932;
const double EPS = 1e-7;
long long gcdEx(long long a, long long b, long long *x, long long *y) {
  if (!a) {
    *x = 0;
    *y = 1;
    return b;
  }
  long long x1, y1, gcd = gcdEx(b % a, a, &x1, &y1);
  *x = y1 - (b / a) * x1;
  *y = x1;
  return gcd;
}
long long modI(long long b, long long m) {
  long long x, y;
  gcdEx(b, m, &x, &y);
  return (x % m + m) % m;
}
long long modD(long long a, long long b) {
  return (modI(b, MOD) * (a % MOD)) % MOD;
}
long long modS(long long a, long long b) {
  return ((a % MOD) - (b % MOD) + MOD) % MOD;
}
long long modP(long long x, long long y) {
  long long r = 1;
  x %= MOD;
  while (y > 0) {
    if (y & 1) {
      r = (r * x) % MOD;
    }
    y = y >> 1;
    x = (x * x) % MOD;
  }
  return r;
}
long long modA(long long a, long long b) {
  return ((a % MOD) + (b % MOD)) % MOD;
}
long long modM(long long a, long long b) {
  return ((a % MOD) * (b % MOD)) % MOD;
}
void solve(int TEST_CASE) {
  int n;
  cin >> n;
  long long r[n][3];
  for (int i = 0; i < (3); ++i)
    for (int j = 0; j < (n); ++j) cin >> r[j][i];
  long long dp[n][2];
  dp[0][0] = r[0][0];
  dp[0][1] = r[0][1];
  for (int i = 1; i <= (n - 1); ++i) {
    dp[i][0] = (long long)max(dp[i - 1][0] + r[i][1], dp[i - 1][1] + r[i][0]);
    dp[i][1] = (long long)max(dp[i - 1][0] + r[i][2], dp[i - 1][1] + r[i][1]);
  }
  if (DEBUGGING)
    for (int i = 0; i < (n); ++i) {
      cout << dp[i][0] << " - " << dp[i][1] << "\n";
    }
  cout << dp[n - 1][0];
}
int main(int argc, char *argv[]) {
  if (argc == 2 && argv[1][1] == 'v') DEBUGGING = 1;
  cin.sync_with_stdio(0);
  cin.tie(0);
  cin.exceptions(cin.failbit);
  int nTestCases = 1;
  for (int i = 1; i <= (nTestCases); ++i) solve(i);
  return 0;
}
