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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int long long
  4.  
  5. int f(int k, int m) {
  6.     if (m <= k) {
  7.         // 1 + 2 + ... + m
  8.         return m * (m + 1) / 2;
  9.     }
  10.     int A = k * (k + 1) / 2;
  11.  
  12.     int r = m - k;          
  13.     int B = r * (2 * k - r + 1) / 2;
  14.  
  15.     return A + B;
  16. }
  17.  
  18. void solve() {
  19.     int k, x;
  20.     cin >> k >> x;
  21.  
  22.     int l = 1, r = 2 * k, ans = r;
  23.  
  24.     while (l <= r) {
  25.         int m = (l + r) / 2;
  26.  
  27.         if (f(k, m) >= x) {
  28.             ans = m;
  29.             r = m - 1;
  30.         } else {
  31.             l = m + 1;
  32.         }
  33.     }
  34.  
  35.     cout << ans << "\n";
  36. }
  37.  
  38. int32_t main() {
  39.     ios::sync_with_stdio(false);
  40.     cin.tie(nullptr);
  41.  
  42.     int t;
  43.     cin >> t;
  44.     while (t--) solve();
  45. }
  46.  
Success #stdin #stdout 0.01s 5300KB
comments (?)
stdin
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7
4 6
4 7
1 2
3 7
2 5
100 1
1000000000 923456789987654321
stdout
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3
4
2
4
3
1
1608737401
https://ideone.com/BZJNII
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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