/*
https://www.youtube.com/watch?v=jlWA73MDrC4
a1*a-a2*(a+d)+a3*(a+2d)-a4(a+3d)+a5(a+4d)....
a1 -a2 +a3 -a4 +a5 .....
for any odd l
suppose from l=3 upto r we want
a3*(a)-a4(a+d)+a5*(a+2d)..
then we:
a3(a+(3-1)*d)-a4(a+(4-1)*d)+..
-
(3-1)d*(a3-a4+a5...)
*/
#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define int long long
int mod=1e9+7;
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