bzoj千题计划173：bzoj1257: [CQOI2007]余数之和sum

#include<cstdio>
#include<iostream>

using namespace std;

int main()
{
    int n,k;
    scanf("%d%d",&n,&k);
    long long ans=0;
    if(n>k) 
    {
        ans=1ll*(n-k)*k;
        n=k;
    }
    int l,r;
    int t;
    for(l=1;l<=n;l=r+1)
    {
        t=k/l; r=k/t;
        if(r>n) r=n;
        ans+=1ll*k*(r-l+1)-1ll*(r-l+1)*(l+r)/2*t;
    }
    cout<<ans;
}