program ABC060C
    implicit none
    integer::n,t,i,l
    integer,allocatable::s(:)
    integer,allocatable::a(:)
    read*,n,t
    allocate(a(n))
    read*,a
    l = t + a(n)
    allocate(s(l))
    s = [(0,i = 1,l )]
    do i = 1,n
        s(a(i)+1:a(i)+t) = 1
    end do
    print*,sum(s)
end program ABC060C