Copy data from two different sheets

[spycein]

Hello Everyone,
I have two sheets with follow data:

Sheet 1
SR. No	Data
1	A
2	B
3	C
4	D
5	E
6	F
7	G
8	H

Sheet 2
SL. No	Data
1	100
2	200
3	300
4	400
5	500
6	600
7	700
8	800

I am looking for a formula/way to copy data from above sheets to a third sheet in following format

Sheet 3
Data
A
100
B
200
C
300
D
400
E
500
F
600
G
700
H
800

I also want to make the process as reference error proof, i.e. if i delete any row in sheet 1 or Sheet 2 then the results in Sheet 3 should not give #REF! error.

Hope i explained my query properly.
Thanks in advance.
Best Regards,