CF1062D Fun with Integers

思路：

找规律。

实现：

 #include <bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 int main()
 {
     ll n;
     while (cin >> n)
     {
         ll cnt = ;
         for (int i = ; i * i <= n; i++)
         {
             ll tmp = n / i;
             cnt += (i +  + tmp) * (tmp - i) / ;
             cnt += (tmp - i + ) * i;
         }
         cout << (cnt << ) << endl;
     }
     return ;
 }