n = int(input())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
c = list(map(int,input().split()))
dp1 = [0]*5; dp2 = [0]*5
for i in range(n):
    dp1[4] = max(dp1[2:5])+a[i]
    dp1[3] = max(dp1[2:4])+b[i]
    dp1[2] = max(dp1[0:3])+c[i]
    dp1[1] = max(dp1[0:2])+b[i]
    dp1[0] = max(dp1[0:1])+a[i]
    dp2[4] = max(dp2[3:5])+a[i]
    dp2[3] = max(dp2[2:4])+b[i]
    dp2[2] = max(dp2[1:3])+a[i]
    dp2[1] = max(dp2[0:2])+b[i]
    dp2[0] = max(dp2[0:1])+a[i]
print(max(dp1+dp2))