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  1. #include <bits/stdc++.h>
  2. #define ll long long
  3. #define fo(i,d,c) for(int i=d;i<=c;i++)
  4. #define IOS ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
  5.  
  6. using namespace std;
  7.  
  8. int a,b;
  9. const int N=1e7;
  10. ll f[N+1];
  11. void sang_uoc(int n)
  12. {
  13.     fo(i,1,n)
  14.     {
  15.         for(int j=i*2;j<=n;j+=i){
  16.             f[j]+=i;
  17.         }
  18.     }
  19. }
  20. int tinh(int n)
  21. {
  22.     if(n!=1){
  23.         int tmp=n-1;
  24.         fo(i,2,sqrt(n)){
  25.             if(n%i==0){
  26.                 tmp-=(i+n/i);
  27.             }
  28.         }
  29.         int sqrt_n=sqrt(n);
  30.         if(sqrt_n*sqrt_n==n){
  31.             tmp+=sqrt_n;
  32.         }
  33.         return abs(tmp);
  34.     }
  35.     else{
  36.         return n;
  37.     }
  38. }
  39. ll solve1(){
  40.     ll res=0;
  41.     fo(i,a,b){
  42.         res+=tinh(i);
  43.     }
  44.     return res;
  45. }
  46. ll solve2()
  47. {
  48.     ll res=0;
  49.     fo(i,a,b){
  50.         res+=abs(i-f[i]);
  51.     }
  52.     return res;
  53. }
  54. int main()
  55. {
  56.     IOS;
  57.     cin>>a>>b;
  58.     if(b<=1e6){
  59.         cout<<(ll)solve1();
  60.     }
  61.     else{
  62.         sang_uoc(N);
  63.         cout<<(ll)solve2();
  64.     }
  65.     return 0;
  66. }
  67.  
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/BYJI4Z
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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