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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     ios::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.  
  8.     int N;
  9.     cin >> N;
  10.  
  11.     long long ans = 0;
  12.  
  13.     // x <= y
  14.     for (int x = 1; x * 2 <= N; x++) {
  15.         for (int y = x; y <= N; y++) {
  16.  
  17.             if ((long long)y * (x + y) > N) break;
  18.             if (__gcd(x, y) != 1) continue;
  19.  
  20.             long long kmax = (long long)N / (y * (x + y));
  21.             ans += kmax;
  22.         }
  23.     }
  24.  
  25.     cout << ans << "\n";
  26.     return 0;
  27. }
  28.  
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/ExGPOm
language:
C++14 (gcc 8.3)
created:
9 hours ago
visibility:
public

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