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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. int phi (int n) {
  5.     int result = n;
  6. 	for (int i=2; i*i<=n; ++i)
  7. 		if (n % i == 0) {
  8. 			while (n % i == 0)
  9. 				n /= i;
  10. 			result -= result / i;
  11. 		}
  12. 		if (n > 1)
  13. 			result -= result / n;
  14. 		return result;
  15. }
  16. int main()
  17. {
  18. 	int n;
  19. 	cin>>n;
  20. 	int res = 2*n*(n+1);
  21. 	for (int i=1;i<=n;i++)
  22. 	{
  23. 		if (i==1)
  24. 		{
  25. 			res+=2*n*n;
  26. 		}
  27. 		else
  28. 			res+=2*(n+1-i)*(2*n+2-i)*phi(i);
  29. 	}
  30. 	res = (n*(n+1)*(n+1)*(n+2)/2 - res);
  31.  	cout<<res<<endl;
  32.  
  33. 	return 0;
  34. }
Success #stdin #stdout 0s 2856KB
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https://ideone.com/OzPUrR
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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