What is duration of F-1 Visa for Hybrid Program?

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I have been accepted into a Hybrid Masters program. This program is of two years and requires four residencies i.e. one residency of around 5 days each semester. What will be the duration of my F-1 visa? Will it be of 2 years or for specific days? If it will be of specific days, will it be issued in each semester when I have to go to US to meet the residency requirement? Seniors please throw some light.