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 C (GCC 5.4.1) (judge verdict: Wrong Answer)


#include <stdio.h>
#include <math.h>


int main(void)
{
	//変数の宣言
	int n,k;
	long long int ans=0;
	int i,j,a,b;
	int temp;
	int ansup=0;
	
	//データの読み込み
	scanf("%d %d",&n,&k);
	
	
//	printf("nは%dです\n", n);
//	printf("データの読み込み終了\n");
	//実際の処理
	
	
	for(b=k+1;b<n+1;b++){
		ans=ans+(n-n%b)*(b-k)/b;
		for(i=1;i<n%b+1;i++){
			if(i+1>k){
				ans++;
			}
		}
		
		if(ans>100000000){
			ansup=ansup+ans/100000000;
			ans=ans%100000000;
		}
	}
		
//	printf("計算部分終了\n");
	
	//出力
	
	printf("%d",ansup);
	printf("%lld",ans);
	
	
//	printf("結果の出力終了\n");
	
	return 0;
}