Problem:
Score : 400 points

Problem Statement

Takahashi had a pair of two positive integers not exceeding N, (a,b), which he has forgotten.
He remembers that the remainder of a divided by b was greater than or equal to K.
Find the number of possible pairs that he may have had.

Constraints

1 \leq N \leq 10^5

0 \leq K \leq N-1

All input values are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the number of possible pairs that he may have had.

Sample Input 1

5 2

Sample Output 1

7

There are seven possible pairs: (2,3),(5,3),(2,4),(3,4),(2,5),(3,5) and (4,5).

Sample Input 2

10 0

Sample Output 2

100

Sample Input 3

31415 9265

Sample Output 3

287927211

Solution in Fortran (gfortran v4.8.4) (judge verdict: Accepted)

program arc091_d
    use,intrinsic :: iso_fortran_env
    implicit none
    integer(int64):: n,k,b,ans=0

    read*, n,k

    do b = k+1,n
        ans=ans+(n/(b)*(b-k))+max((n-((n/b)*b+k)+1),0)
    end do
    if (k==0) ans=ans-n
    print'(i0)', ans
end program arc091_d