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  1. #include <bits/stdc++.h>
  2. #define mod 1000000007
  3. #define ll unsigned long long
  4.  
  5. using namespace std;
  6. ll func(ll a,ll b)
  7. {
  8.     long long int l=(2*a-b-1);
  9.     if((l%(b-a))==0)
  10.     {
  11.         return (b-a)%mod;
  12.     }
  13.     else
  14.     {
  15.         ll k= l%(b-a);
  16.         return k;
  17.     }
  18. }
  19. int main()
  20. {
  21.    ll t;
  22.    cin>>t;
  23.    while(t--)
  24.    {
  25.        ll n,k,a,b,k1;
  26.        long long int l;
  27.        cin>>n>>k;
  28.        a=k;
  29.        b=k+n-1;
  30.        l=(2*a-b-1);
  31.        ll s=(a-1)%mod;
  32.        if(l<=0)
  33.        {
  34.            s=s%mod;
  35.        }
  36.        else{
  37.         ll a1=func(a,b);
  38.         k1=(l-a1)/(n-1);
  39.         k1++;
  40.         k1=(k1*(a1+l));
  41.         k1=k1/2;
  42.         k1=k1%mod;
  43.         s=s+k1;
  44.        }
  45.        cout<<s%mod<<endl;
  46.    }
  47. }
  48.  
Success #stdin #stdout 0s 15232KB
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https://ideone.com/u5rQCP
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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