Score : $400$ points
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.
Input is given from Standard Input in the following format:
Print the number of possible pairs that he may have had.
There are seven possible pairs: $(2,3),(5,3),(2,4),(3,4),(2,5),(3,5)$ and $(4,5)$.