counting duplicates with several conditions

[Johanna Reilly]

Hi I have data that looks like this:

ID	City
1	Glasgow
2	Dundee
3	Edinburgh
3	Edinburgh
3	Dundee
4	Glasgow
4	Glasgow
4	Glasgow
5	Edinburgh
6	Dundee
6	Edinburgh

Each ID is a person and each line is at a specific point in time where the information was collected. What I would like to do is count the number of people of move cities during the time period. So when the ID in column 1 is the same but the city if different. I've tried using COUNTIF but can't seem to figure it out can anyone help with a formula that might do this? 

Thanks

Jo

[#2]

For example, what results do you expect to be returned by the formula in Column C?

[#3]

I just want to find the total number of people who have a change of city on the spreadsheet @Twifoo 

[#4]

In your sample data, what specific result do you expect as the answer to your question?