1967135_ac_578ms_44k.c

北大大牛代码 1240道题的原代码 超级权威

# include <stdio.h>

int main()
{
	__int64 n, k, i, t, tmp;
	__int64 sum;

	while(scanf("%I64d%I64d",&n,&k)==2)
	{
		sum = 0;
		if(k < n)
		{
			sum = (n-k)*k;
			n = k-1;
		}
		t = 1;
		while(1)
		{
			tmp=k/(t+1)+1;
			if(n<=500000)
				break;
			if(tmp>n)
				{t++;continue;}
			sum+=k*(n-tmp+1)-t*(n-tmp+1)*(tmp+n)/2;
			n = tmp-1;
			t++;
		}
		for(i = 2; i <= n; i++)
		    sum += k%i;
		printf("%I64d\n",sum);
	}
	return 1;
}