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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. typedef long long ll;
  4. int main() {
  5. 	int t;
  6. 	scanf("%d", &t);
  7. 	while(t--) {
  8. 		int a, n;
  9. 		scanf("%d%d", &n, &a);
  10. 		int l = 0, r = n, mid, res = -1;
  11. 		while(l <= r) {
  12. 			mid = (l + r) / 2;
  13. 			if((ll)n*a - (ll)mid*(mid+1)/2 >= n-mid) {
  14. 				res = mid;
  15. 				l = mid + 1;
  16. 			} else r = mid - 1;
  17. 		}
  18. 		printf("%d\n", res);
  19. 	}
  20. 	return 0;
  21. }
Success #stdin #stdout 0s 4176KB
comments (?)
stdin 
3
2 4
5 1
8 4
stdout 
2
1
7
https://ideone.com/VNyo8h
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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