bzoj 1257: [CQOI2007]余数之和sum

题目大意：

题解：

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#define LL long long
using namespace std;
LL sum(int l,int r){return (LL)(r-l+1)*(LL)(l+r)/2;}
int main()
{
int n,k;scanf("%d %d",&n,&k);
LL ans=0;int pos;
for(int i=1;i<=n;i=pos+1)
{
if(k/i==0) pos=n;
else pos=min((k/(k/i)),n);
ans+=(LL)k*(pos-i+1)-(LL)(k/i)*sum(i,pos);
}
printf("%lld",ans);
}