A New Function LightOJ - 1098（）

#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define Pair pair<int, int>
#define rap(a, n) for(int i=a; i<=n; i++)
#define mem(a, b) memset(a, b, sizeof(a))
#define _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int maxn = 10010, INF = 0x7fffffff;

int main()
{
    int T, kase = 0;
    cin >> T;
    while(T--)
    {
        LL n, res = 0;
        cin >> n;
        LL m = sqrt(n+0.5);
        rap(2, m)
        {
            res += (n / i - 1)* i;
            if(n/i > m)
            {
               LL p = n/i;
               res += (p - m) * (m+1+p) / 2;  //等差数列求和公式
            }
        }
        cout<< "Case "<< ++kase << ": "<< res <<endl;

    }


    return 0;
}