解题思路
多年以前get到的新技能,水篇博客以示敬意。
代码:
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<string>
#include<cmath>
#include<cstdio>
#define ll long long
using namespace std;
ll n,m,k,r,ans;
int main(){
scanf("%lld%lld",&n,&k);
if(n>k) {m=n-k;n=k;}
for(int i=1;i<=n;i=r+1){
r=k/(k/i);if(r>n) r=n;
ans+=k/i*(r+i)*(r-i+1)/2;
}
ans=k*(m+n)-ans;
printf("%lld",ans);
return 0;
}