N = int(input())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
C = list(map(int,input().split()))

INF = 10**18
dp = [[[-INF for _ in range(3)] for _ in range(3)] for _ in range(N+1)]
dp[0][0][0] = 0
for i in range(N):
    dp[i+1][0][0] = dp[i][0][0] + A[i]
    dp[i+1][0][1] = max(dp[i][0][0], dp[i][0][1]) + B[i]
    dp[i+1][0][2] = max(dp[i][0][0], dp[i][0][1], dp[i][0][2]) + C[i]

    dp[i+1][1][0] = max(dp[i][0][1], dp[i][1][0]) + A[i]
    dp[i+1][1][1] = max(dp[i][0][1], dp[i][0][2], dp[i][1][0], dp[i][1][0], dp[i][1][1]) + B[i]

    dp[i+1][2][0] = max(dp[i][0][2], dp[i][1][1], dp[i][2][0]) + A[i]

print(max(max(i) for i in dp[-1]))