Identify two or more are same or not in Excel

Hi Everyone,
I have an excel formula question that someone might can help me with.

A B
1 <- A1 True
1 <- A2 True
1 <- A3 True
4 <- A4 False
2 <- A5 True
2 <- A6 True

Using IF command, how would I show that above data to identify the same datas and returns me with message showing true or false on column B?
As you see above, A1, A2, A3 are same with data 1 and A5 and A6 are same with data 2.
I need to have compare between different rows, row before and row after and if any of the data is same then the returning value on B would be true.
If row before or after doesn't contain same data then the returning value on B would be false.
I hope my question is not too confusing.
Thanks