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  1. #include<iostream>
  2. using namespace std;
  3. int main(){
  4. 	while(1){
  5. 		int n; cin >> n;
  6. 		if(n==0){
  7. 			return 0;
  8. 		} 
  9. 		else if(n==1){
  10. 			cout << 1;
  11. 		}
  12. 		else{
  13. 			int list[1000002]={};
  14. 			for(int x=2; x<=2*n; x++){
  15. 				for(int i=x+x; i<=n; i+=x){
  16. 					if(list[i]!=1){
  17. 						list[i]=1;
  18. 					}
  19. 				}
  20. 			}
  21. 			list[1]=1;
  22. 			int i=0, ans[1000002]={};
  23. 			for(int x=n; x<=2*n; x++){
  24. 				if(list[x]==0) i++;
  25. 			}
  26. 			cout << i << "\n";
  27. 		}
  28. 	}
  29. }
Success #stdin #stdout 0s 7500KB
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https://ideone.com/MxSrux
language:
C++ (gcc 8.3)
created:
4 years ago
visibility:
public

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