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  1. #include<bits/stdc++.h>
  2. #define file ""
  3.  
  4. using namespace std;
  5.  
  6. #define int long long
  7. #define ld long double
  8. #define pii pair<int,int>
  9. #define pb push_back
  10. #define mp make_pair
  11. #define X first
  12. #define Y second
  13. #define lb lower_bound
  14. #define ub upper_bound
  15. #define all(x) x.begin(), x.end()
  16. #define sz(x) x.size()
  17.  
  18. const int N=1e6+5;
  19. const int NN=1e3+9;
  20. const int MOD=1e9+7;
  21. const int dx[4]={0, -1, 0, 1};
  22. const int dy[4]={-1, 0, 1, 0};
  23. const int INF=1e18;
  24. const ld eps=1e-6;
  25. const ld pi=acos(-1.0); // 48 digits
  26.  
  27. int n, inv;
  28.  
  29. int Pow(int a, int b) {
  30.     if (b==0) return 1;
  31.     if (b==1) return a;
  32.     int tmp=Pow(a,b/2)%MOD;
  33.     if (b&1) return (((tmp*tmp)%MOD)*a)%MOD;
  34.     return (tmp*tmp)%MOD;
  35. }
  36.  
  37. int Sum_range(int n) {
  38.     n%=MOD;
  39.     int res=(((n*(n+1))%MOD)*inv)%MOD;
  40.     return res;
  41. }
  42.  
  43. int Sum(int n) {
  44.     int res=0;
  45.     int l=1;
  46.     int r=1;
  47.     while (l<=n) {
  48.         int same=n/l;
  49.         r=n/same;
  50.         int tmp1=((Sum_range(r)-Sum_range(l-1))%MOD+MOD)%MOD;
  51.         int tmp2=(same*tmp1)%MOD;
  52.         res=(res+tmp2)%MOD;
  53.         l=r+1;
  54.     }
  55.     return res;
  56. }
  57.  
  58. void process() {
  59.     // Code here :V
  60.     cin>>n;
  61.     inv=Pow(2,MOD-2);
  62.     cout<<Sum(n);
  63.  
  64. }
  65.  
  66. signed main() {
  67.     cin.tie(0)->sync_with_stdio(0);
  68. //    freopen(file".inp","r",stdin);
  69. //    freopen(file".out","w",stdout);
  70.     int t=1;
  71. //    cin>>t;
  72.     while (t--) process();
  73.     return 0;
  74. }
  75.  
Success #stdin #stdout 0.05s 5288KB
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https://ideone.com/O2rSbY
language:
C++14 (gcc 8.3)
created:
9 hours ago
visibility:
public

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