n = int(input())
a = [int(x) for x in input().split()]
b = [int(x) for x in input().split()]
c = [int(x) for x in input().split()]

# 0: [0]
# 1: [0|1]
# 2: [0|1|0]
# 3: [0|1|2]
# 4: [0|1|0|1]
# 5: [0|1|2|1]
# 6: [0|1|0|1|0]
# 7: [0|1|2|1|0]

ans = [-10 ** 15] * 8
ans[0] = 0
for i in range(n):
	nxt = [0] * 8
	
	nxt[0] = ans[0] + a[i]
	nxt[1] = max(ans[0], ans[1]) + b[i]
	nxt[2] = max(ans[1], ans[2]) + a[i]
	nxt[3] = max(ans[1], ans[3]) + c[i]
	nxt[4] = max(ans[2], ans[4]) + b[i]
	nxt[5] = max(ans[3], ans[5]) + b[i]
	nxt[6] = max(ans[4], ans[6]) + a[i]
	nxt[7] = max(ans[5], ans[7]) + a[i]
	
	ans = nxt
	
print(max(ans))