LightOJ 1245 数学题，找规律

#include<iostream>
#include<cstring>
#include<cmath>
#include<queue>
#include<algorithm>
#include<cstdio>
#define max(a,b) a>b?a:b
#define F(i,a,b) for (int i=a;i<=b;i++)
#define mes(a,b) memset(a,b,sizeof(a))
#define INF 0x3f3f3f3f
#define LL long long
using namespace std;
const int N=10010,MAX=1000100;

LL Har(LL n)
{
    LL sum=0,sq=sqrt(n);
    F(i,1,sq){
        sum=sum+(n/i-n/(i+1))*i+n/i;  //恶心到炸
    }
    if(sq==n/sq){   //注意
        sum-=sq;
    }
    return sum;
}

int main()
{
    int t;
    LL n;
    scanf("%d",&t);
    F(cas,1,t){
        scanf("%lld",&n);
        printf("Case %d: %lld\n",cas,Har(n));
    }

    return 0;
}