CF985D Sand Fortress

思路：

很奇怪的结论题，不好想。参考了http://codeforces.com/blog/entry/59623

实现：

 #include <bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 const ll INF = 0x7f7f7f7f;
 ll n, H;
 bool check(ll m)
 {
     ll tmp = min(m, H);
     return m * m - tmp * (tmp - ) /  <= n;
 }
 ll solve(ll n, ll H)
 {
     ll l = , r = INF, ans = -;
     while (l <= r)
     {
         ll m = l + r >> ;
         if (check(m))
         {
             ans = m;
             l = m + ;
         }
         else r = m - ;
     }
     return ans;
 }
 int main()
 {
     while (cin >> n >> H)
     {
         ll k = solve(n, H);
         ll t = min(k, H);
         ll ans =  * k -  - t;
         ll rem = n - (k * k - t * (t - ) / );
         ans += (rem + k - ) / k;
         cout << ans +  << endl;
     }
     return ;
 }