• Source 
    1. #include <iostream>
    2. #include <cstdio>
    3. using namespace std;
    4. typedef unsigned long long ll;
    5. int main()
    6. {
    7. 	ll t;
    8. 	scanf("%lld",&t);
    9. 	for(ll k=0;k<t;++k)
    10. 	{
    11. 		ll n;
    12. 		scanf("%lld",&n);
    13. 		--n;
    14. 		ll n1,n2,n3;
    15. 		n1=n/3;
    16. 		n2=n/5;
    17. 		n3=n/15;
    18. 		ll ans;
    19. 		ans=(3*n1*(n1+1))/2+(5*n2*(n2+1))/2-(15*n3*(n3+1))/2;
    20. 		printf("%lld\n",ans);
    21. 	}
    22. 	return 0;
    23. }