from collections import *
import sys
import heapq
from heapq import heapify, heappop, heappush
import bisect
from bisect import bisect_left, bisect_right
import itertools
from functools import lru_cache
from types import GeneratorType
from fractions import Fraction
import math
import copy
import random

# import numpy as np

# sys.setrecursionlimit(int(1e7))
# @lru_cache(maxsize=None) # CPython特化
# @bootstrap # PyPy特化(こっちのほうが速い) yield dfs(), yield Noneを忘れずに


def bootstrap(f, stack=[]):  # yield
    def wrappedfunc(*args, **kwargs):
        if stack:
            return f(*args, **kwargs)
        else:
            to = f(*args, **kwargs)
            while True:
                if type(to) is GeneratorType:
                    stack.append(to)
                    to = next(to)
                else:
                    stack.pop()
                    if not stack:
                        break
                    to = stack[-1].send(to)
            return to

    return wrappedfunc


dxdy1 = ((0, 1), (0, -1), (1, 0), (-1, 0))  # 上下右左
dxdy2 = (
    (0, 1),
    (0, -1),
    (1, 0),
    (-1, 0),
    (1, 1),
    (-1, -1),
    (1, -1),
    (-1, 1),
)  # 8方向すべて
dxdy3 = ((0, 1), (1, 0))  # 右 or 下
dxdy4 = ((1, 1), (1, -1), (-1, 1), (-1, -1))  # 斜め
INF = float("inf")
_INF = 1 << 60
MOD = 998244353
mod = 998244353
MOD2 = 10**9 + 7
mod2 = 10**9 + 7
# memo : len([a,b,...,z])==26
# memo : 2^20 >= 10^6
# 小数の計算を避ける : x/y -> (x*big)//y  ex:big=10**9
# @:小さい文字, ~:大きい文字,None: 空の文字列
# ユークリッドの互除法：gcd(x,y)=gcd(x,y-x)
# memo : d 桁以下の p 進表記を用いると p^d-1 以下のすべての
#        非負整数を表現することができる
# memo : (X,Y) -> (X+Y,X−Y) <=> 点を原点を中心に45度回転し、√2倍に拡大
# memo : (x,y)のx正から見た偏角をラジアンで(-πからπ]：　math.atan2(y, x)
# memo : a < bのとき ⌊a⌋ ≦ ⌊b⌋

input = lambda: sys.stdin.readline().rstrip()
mi = lambda: map(int, input().split())
li = lambda: list(mi())
ii = lambda: int(input())
py = lambda: print("Yes")
pn = lambda: print("No")
pf = lambda: print("First")
ps = lambda: print("Second")

N = ii()
A = li()
B = li()
C = li()
dp = [[0] * 5 for _ in range(N + 1)]
for i in range(N):
    for j in range(5):
        tmp = 0
        for k in range(j + 1):
            tmp = max(tmp, dp[i][k])
        if j == 0 or j == 4:
            dp[i + 1][j] = tmp + A[i]
        if j == 1 or j == 3:
            dp[i + 1][j] = tmp + B[i]
        if j == 2:
            dp[i + 1][j] = tmp + C[i]

dp2 = [[0] * 5 for _ in range(N + 1)]
for i in range(N):
    for j in range(5):
        tmp = 0
        for k in range(j + 1):
            tmp = max(tmp, dp2[i][k])
        if j == 0 or j == 2 or j == 4:
            dp2[i + 1][j] = tmp + A[i]
        if j == 1 or j == 3:
            dp2[i + 1][j] = tmp + B[i]
print(max(max(dp[-1]), max(dp2[-1])))