Absence Periods Calculation

Can you help, I have attached an absence sheet which shows each employee number and each period of absence - start and end date.

I need a formulae which will show how many periods of absence each employee has had bearing in mind all employees are on the same sheet. For example, staff no 88 should show as 2 periods of absence as the first four absences are linked, the formulae should then move on to the next staff no and count again

Hope this makes sense

Any help is appreciated