# dp[i][k] = i枚目まで見たときに、その状態がk = 0:片面焼き開始前、1:片面焼き開始後、2:両面焼き中、3:両面焼き終了片面中、4:片面終了後
N = int(input())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
C = list(map(int,input().split()))
INF = 1 << 60
dp = [[-INF] * 5 for i in range(N)]

# 起こり得る状態を設定
dp[0][0] = A[0]
dp[0][1] = B[0]
dp[0][2] = C[0]

for i in range(1, N):
    dp[i][0] = dp[i - 1][0] + A[i]
    
    dp[i][1] = max(dp[i - 1][0], dp[i - 1][1]) + B[i]
    
    dp[i][2] = max(dp[i - 1][1], dp[i - 1][2]) + C[i]
    
    dp[i][3] = max(dp[i - 1][2], dp[i - 1][3]) + B[i]
    
    dp[i][4] = max(dp[i - 1][3], dp[i - 1][4]) + A[i]
    
print(max(dp[-1]))