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  1. #include <bits/stdc++.h>
  2. #define int long long
  3. using namespace std;
  4.  
  5. unordered_map<int, int> memo;
  6.  
  7. int S(int n) {
  8.     if (n == 0) return 0;
  9.     if (memo.count(n)) return memo[n];
  10.  
  11.     int ans = n * (n + 1) / 2;
  12.     int i = 2;
  13.     while (i <= n) {
  14.         int q = n / i;
  15.         int r = n / q;
  16.         ans -= (r - i + 1) * S(q);
  17.         i = r + 1;
  18.     }
  19.     return memo[n] = ans;
  20. }
  21.  
  22. main() {
  23.     ios::sync_with_stdio(false);
  24.     cin.tie(nullptr);
  25.  
  26.     int N, D;
  27.     cin >> N >> D;
  28.  
  29.     int M = N / D;
  30.     cout << S(M);
  31. }
  32.  
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/KM4oJW
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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