Write two functions for each of the following $($a recursive function and an

iterative function$)$:

$1-$ calculate the Fibonacci$$s number of the following equation

F$(1)=3$

F$(2)=4$

F$(3)=5$

F$($n$)=$ F$($n$-1)+$ F$($n$-2)-$ F$($n$-3)$