LOJ_1245 - Harmonic Number (II)

#include<cstdio>
#include<sstream>
#include<cstdlib>
#include<cctype>
#include<cmath>
#include<algorithm>
#include<set>
#include<queue>
#include<stack>
#include<list>
#include<iostream>
#include<fstream>
#include<numeric>
#include<string>
#include<vector>
#include<cstring>
#include<map>
#include<iterator>
using namespace std;

int main(void){
    // freopen("//home//mazhar//Desktop//in.txt","r",stdin) ;
     int tc,ct=1;
     unsigned long long int  res,n,i,p;
     scanf("%d",&tc) ;
     while(tc--){
         scanf("%llu",&n) ;
         i = 1 ;
         p = 0 ;
         res = 0 ;
         int k =sqrt(n) ;
         for(i=1;i<=k;i++){
             res = res+i*((n/i)-(n/(i+1)))+n/i ;
             p = p+(n/i)-(n/(i+1))+1 ;
            // cout<<res<<endl ;
         }
         res = res+(n-p)*(n/k) ;

         printf("Case %d: %llu\n",ct++,res) ;


     }


   return 0 ;

}