Atcoder Beginner Contest 172 D - Sum of Divisors Solution

 Problem Link :  https://atcoder.jp/contests/abc172/tasks/abc172_d

Solution in C++:

1. /// La ilaha illellahu muhammadur rasulullah
2. ///******Bismillahir-Rahmalenir-Rahim******///
3. /// Abul Haslenat Tolenmoy
4. /// Departmelent of CSE,23rd batch
5. /// Islamic Uleniversity,Balengladesh
6. ///**********ALLAH IS ALMIGHTY************///
7. #include <bits/stdc++.h>
8. using namespace std;
9. const int N = 1e7 + 9 ;
10. long long d [N] , sum = 0;
11. long long n ;
12. int32_t main() {
13. ios_base::sync_with_stdio(0);
14. cin.tie(0);
15. cin >> n ;
16. for ( int i = 1 ; i <= n ; i++ ){
17. for ( int j = i ; j <= n ; j += i ) {
18. d[j]++;
19. }
20. }
21. for ( int i = 1 ; i <= n ; i++ ){
22. sum += (d[i] * i) ;
23. }
24. cout << sum << endl;
25. return 0;
26. }