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

dp = [[-10**18]*5 for _ in range(N+1)]

for j in range(5):
    dp[0][j] = 0

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

    dp[i+1][2] = max(dp[i+1][2], dp[i][2] + C[i])
    dp[i+1][3] = max(dp[i+1][3], dp[i][2] + C[i])

    dp[i+1][3] = max(dp[i+1][3], dp[i][3] + B[i])
    dp[i+1][4] = max(dp[i+1][4], dp[i][3] + B[i])

    dp[i+1][4] = max(dp[i+1][4], dp[i][4] + A[i])

ans1 = max(dp[N])

dp_ = [[-10**18]*5 for _ in range(N+1)]

for j in range(5):
    dp_[0][j] = 0

for i in range(N):
    dp_[i+1][0] = max(dp_[i+1][0], dp_[i][0] + A[i])
    dp_[i+1][1] = max(dp_[i+1][1], dp_[i][0] + A[i])
        
    dp_[i+1][1] = max(dp_[i+1][1], dp_[i][1] + B[i])
    dp_[i+1][2] = max(dp_[i+1][2], dp_[i][1] + B[i])

    dp_[i+1][2] = max(dp_[i+1][2], dp_[i][2] + A[i])
    dp_[i+1][3] = max(dp_[i+1][3], dp_[i][2] + A[i])

    dp_[i+1][3] = max(dp_[i+1][3], dp_[i][3] + B[i])
    dp_[i+1][4] = max(dp_[i+1][4], dp_[i][3] + B[i])

    dp_[i+1][4] = max(dp_[i+1][4], dp_[i][4] + A[i])

ans2 = max(dp_[N])

print(max(ans1, ans2))