PROGRAM ATCODER

implicit none
integer(8) :: k, a, b, c, k_zanki, all, i

read(*,*) k, a, b

if(b-a <= 2) then 
	write(*,'(i0)') k+1
    stop
end if

k_zanki = k - (a-1)

all = a
do i = 1, k_zanki/2
	all = all + b - a
end do

if(mod(k_zanki,2) == 1)then
	all = all +1
end if

write(*,'(i0)') all

END PROGRAM ATCODER
