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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. constexpr int mod = 1e9 + 7;
  6. int n,m,id;
  7. int div0, div1;
  8. long long ans = 1;
  9.  
  10. void getdiv(){
  11.     for(int i = 1; i*i <= id; ++i){
  12.         if(id % i == 0){
  13.             div0 += 2;
  14.             if(i*i == id) --div0;
  15.         }
  16.     }
  17.     --div0;
  18. }
  19.  
  20. int main()
  21. {
  22.     ios_base::sync_with_stdio(false);
  23.     cin.tie(0);
  24.     cout.tie(0);
  25.     cin >> n >> m >> id;
  26.     getdiv();
  27.  
  28.     div1 = m/id - 1;
  29.     if(div0-n+1 < 0 or div1 - n + 1 < 0){
  30.         cout << 0;
  31.         return 0;
  32.     }
  33.     for(int i = div0; i > max(div0-n+1, 0); --i){
  34.         ans *= i;
  35.         //cout << i << " " << ans << "\n";
  36.         ans %= mod;
  37.     }
  38.     for(int i = div1; i > max(div1-n+1,0); --i){
  39.         ans *= i;
  40.         ans %= mod;
  41.     }
  42.     ans *= 2;
  43.     if(ans > mod) ans -= mod;
  44.     cout << ans << '\n';
  45.     return 0;
  46. }
Runtime error #stdin #stdout 0s 4396KB
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Standard input is empty
stdout
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Standard output is empty
https://ideone.com/HFZ5iZ
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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