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Farjana_akter

Untitled

Mar 20th, 2019
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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. #define x 10000000
  4. bool mark[x+5]={false};
  5. vector<int>isprime;
  6. void sieve()
  7. {
  8. int i,j,k=0;
  9. mark[0]=true;
  10. mark[1]=true;
  11. for(i=2;i*i<=x;i++)
  12. {
  13. if(mark[i]==false)
  14. {
  15. for(j=i*i;j<=x;j+=i)
  16. mark[j]=true;
  17. }
  18. }
  19. for(i=2;i<=x;i++){
  20. if(mark[i]==false){
  21. isprime.push_back(i);
  22. }
  23. }
  24. }
  25.  
  26. int main()
  27. {
  28. sieve();
  29. long long int n,i,l,j,k,a,b,c,t;
  30. cin>>t;
  31. for(l=1;l<=t;l++)
  32. {
  33. cin>>n;
  34. int count=0;
  35. for(i=0;isprime[i]+isprime[i]<=(n);i++)
  36. {
  37. if(mark[n-isprime[i]]==false)
  38. count++;
  39. }
  40. cout<<"Case "<<l<<": "<<count<<endl;
  41. }
  42. return 0;
  43. }
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