Tinh ham mu va to hop mod p

1. #include <bits/stdc++.h>
2. #define INF 3000000000000000000
3. #define N 200005
4. #define range 1000001
5. #define mod 998244353
6. #define pb push_back
7. #define file freopen("file.inp","r",stdin); freopen("file.out","w",stdout);
8. #define ll long long
9. #define fi first
10. #define se second
11. #define mp make_pair
12. #define PI 3.1415926535
13. using namespace std;
14.  
15. ll f[1000000];
16.  
17. ll mu(ll a,ll n)
18. {
19. ll res=a,ans=1;
20. while (n)
21. {
22. if (n%2)
23. ans=ans*res%mod;
24. res=res*res%mod;
25. n/=2;
26. }
27. return ans;
28. }
29. ll C(ll k,ll n)
30. {
31. return f[n] * mu(f[n-k],mod-2) %mod * mu(f[k],mod-2) %mod;
32. }
33.  
34. int main()
35. {
36. ios_base::sync_with_stdio(false);
37. cin.tie(NULL);
38. cout.tie(NULL);
40. f[0]=1;
41. for (int i=1;i<=500005;i++)
42. f[i]=f[i-1]*i%mod;
44. int n,k;
45. cin>>n>>k;
47. ll ans=0;
48. for (int j=1;n/j-1>=k-1;j++)
49. ans=(ans+C(k-1,n/j-1))%mod;
51. cout<<ans;
52. }
1.