lightoj1007Mathematically Hard

 1 //Accepted    40148 KB    712 ms
 2 #include <cstdio>
 3 #include <cstring>
 4 const int MAXN = 5000005;
 5 unsigned long long phi[MAXN];
 6 void getphi()
 7 {
 8     phi[1]=0;
 9     for (int i=2;i<MAXN;i++)
10     {
11         if (!phi[i])
12         {
13             for (int j=i;j<MAXN;j+=i)
14             {
15                 if (!phi[j])
16                 {
17                     phi[j]=j;
18                 }
19                 phi[j]=phi[j]/i*(i-1);
20             }
21         }
22     }
23     for (int i=2;i<MAXN;i++)
24     phi[i]=phi[i-1]+phi[i]*phi[i];
25 }
26 int main()
27 {
28     getphi();
29     int T;
30     scanf("%d",&T);
31     int a,b;
32     for (int t=1;t<=T;t++)
33     {
34         scanf("%d%d",&a,&b);
35         if (a>b)
36         {
37             t=a;
38             a=b;
39             b=t;
40         }
41         printf("Case %d: %llu\n",t,phi[b]-phi[a-1]);
42     }
43     return 0;
44 }