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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3.  
  4. typedef long long Int;
  5. Int sqr(int x) { return (Int) x*x; }
  6.  
  7. int main()
  8. {
  9. 	int n;
  10. 	cin >> n;
  11. 	Int ans = 0;
  12. 	for (int side = 1; side <= n; side++) {
  13. 		int first = (side+2)/2 ; //2*first-1 >= x
  14. 		int last = n-side+1;
  15. 		if (first > last) break;
  16. 		Int cnt = sqr(last) - sqr(first-1) - (Int) (side-1) * (last-first+1);
  17. 		ans += cnt;
  18. 	}
  19. 	cout << ans;
  20. }
  21.  
Success #stdin #stdout 0.01s 5664KB
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https://ideone.com/BQVwE0
language:
C++14 (clang 8.0)
created:
2 years ago
visibility:
secret

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