C - Aladdin and the Flying Carpet

 #include<bitset>
 #include<map>
 #include<vector>
 #include<cstdio>
 #include<iostream>
 #include<cstring>
 #include<string>
 #include<algorithm>
 #include<cmath>
 #include<stack>
 #include<queue>
 #include<set>
 #define inf 0x3f3f3f3f
 #define mem(a,x) memset(a,x,sizeof(a))

 using namespace std;
 typedef long long ll;

 //输入挂
 inline ll in()
 {
     ll res=;char c;
     while((c=getchar())<'' || c>'');
     while(c>='' && c<='')res=res*+c-'',c=getchar();
     return res;
 }

 const int N=;
 ll prime[];
 int p;
 bitset<N> vis;

 void init()
 {
     for(int i=;i<N;i++)
     {
         if(!vis[i])
         {
             prime[p++]=i;
             for(int j=i+i;j<N;j+=i)
             {
                 vis[j]=;
             }
         }
     }
 }
 int main()
 {
     int T = in();
     int ii = ;
     init();
     while(T--)
     {
         ll area = in(),min_side = in();
         if(min_side >= sqrt(area)){
             printf("Case %d: %d\n",ii++,);
             continue;
         }
         ll tmp = area;
         int ans = ;
         for(int i = ;i < p && prime[i]*prime[i] <= area;i++)
         {
             int cnt = ;
             while(area%prime[i] == )
             {
                 area /= prime[i];
                 cnt++;
             }
             ans *= (cnt+);
         }
         if(area != ) ans <<= ;
         ans >>= ;  //因数的个数除以二就是组数，同时排除了平方根
         for(int i = ;i < min_side;i++)
             if(tmp%i == ) ans--; //min_side此时是小于sqrt（area）的
         printf("Case %d: %d\n",ii++,ans);
     }
     return ;
 }