【ZJNU-2424】求[a,b]之间每个数的因子和的和

/****************************
* Author : W.A.R            *
* Date : 2020-09-12-19:22   *
****************************/
/*
ZJNU-2424
求[a,b]之间每个数的因子和的和
枚举[1,1e6]之间的因子，根据因子确定与之对应的另一个因子求和即可
需要注意的是去重，计算方式要满足不能重复计算因子
http://acm.zjnu.edu.cn/CLanguage/contests/1168/problems/1002.html 
*/
#pragma GCC optimize("O3")
#pragma G++ optimize("O3")
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<iostream>
#include<algorithm>
#include<queue>
#include<map>
#include<stack>
#include<string>
#include<set>
#define mem(a,x) memset(a,x,sizeof(a))
#define Rint register int
using namespace std;
typedef long long ll;
const int maxn=1e6+10;
const int maxm=2e6+10;
const ll mod=1e9+7;

namespace Fast_IO{
    const int MAXL((1 << 18) + 1);int iof, iotp;
    char ioif[MAXL], *ioiS, *ioiT, ioof[MAXL],*iooS=ioof,*iooT=ioof+MAXL-1,ioc,iost[55];
    char Getchar(){
        if (ioiS == ioiT){
            ioiS=ioif;ioiT=ioiS+fread(ioif,1,MAXL,stdin);return (ioiS == ioiT ? EOF : *ioiS++);
        }else return (*ioiS++);
    }
    void Write(){fwrite(ioof,1,iooS-ioof,stdout);iooS=ioof;}
    void Putchar(char x){*iooS++ = x;if (iooS == iooT)Write();}
    inline int read(){
        int x=0;for(iof=1,ioc=Getchar();(ioc<'0'||ioc>'9')&&ioc!=EOF;)iof=ioc=='-'?-1:1,ioc=Getchar();
		if(ioc==EOF)exit(0);
        for(x=0;ioc<='9'&&ioc>='0';ioc=Getchar())x=(x<<3)+(x<<1)+(ioc^48);return x*iof;
    }
    inline long long read_ll(){
        long long x=0;for(iof=1,ioc=Getchar();(ioc<'0'||ioc>'9')&&ioc!=EOF;)iof=ioc=='-'?-1:1,ioc=Getchar();
		if(ioc==EOF)exit(0);
        for(x=0;ioc<='9'&&ioc>='0';ioc=Getchar())x=(x<<3)+(x<<1)+(ioc^48);return x*iof;
    }
    template <class Int>void Print(Int x, char ch = ''){
        if(!x)Putchar('0');if(x<0)Putchar('-'),x=-x;while(x)iost[++iotp]=x%10+'0',x/=10;
        while(iotp)Putchar(iost[iotp--]);if (ch)Putchar(ch);
    }
    void Getstr(char *s, int &l){
        for(ioc=Getchar();ioc==' '||ioc=='
'||ioc=='	';)ioc=Getchar();
		if(ioc==EOF)exit(0);
        for(l=0;!(ioc==' '||ioc=='
'||ioc=='	'||ioc==EOF);ioc=Getchar())s[l++]=ioc;s[l] = 0;
    }
    void Putstr(const char *s){for(int i=0,n=strlen(s);i<n;++i)Putchar(s[i]);}
} // namespace Fast_IO 
using namespace Fast_IO;

int main(){
	ll a=read_ll(),b=read_ll(),ans=0;
	for(ll i=1;i*i<=b;i++){
		ll l=a/i+(a%i!=0),r=b/i;
		l=max(i,l);
		ans+=((l+r)*(r-l+1)/2+(r-l+1)*i);
		if(l==i)ans-=i;
	}
	printf("%lld
",ans);
	return 0;
}