#include <iostream>
using namespace std;
int s, e, tts = 1, tong, so = 1, tt = 1;
const int MOD = 10e9 + 7;
int main() 
{
    cin >> s >> e;
    while(tts <= e)
    {
        if(tts >= s)
            tong += so;
        if(tt == so)
        {
            so += 1;
            tt = 0;
        }
        tt++;
        tts++;
    }
    cout << tong % MOD;
    return 0;
}

$#khanhtaon$

#include <iostream>
using namespace std;
int s,e,t=1,tong=0,so=1,t2=1;
const int m=1e9+7;
int main() {
cin>>s>>e;
while (t<=e) {
if (t>=s) tong+=so;
if (t2==so) so++,t2=0;
t2++,t++;
}
cout<<tong%m;
return 0;
}