program test
implicit none
  integer,allocatable::a(:)
  integer :: N,i,ans
  read*,N
  allocate(a(N))
  read(*,*)(a(i),i=1,N-1)
  ans=a(1)
  do i=1,N-2
  	ans=ans+min(a(i),a(i+1))
  end do
  ans=ans+a(N-1)
 print*,ans
end program
  