Light OJ 1007

#include<bits/stdc++.h>
using namespace std;
const int maxn = 5000000 + 131;
typedef unsigned long long LL;

bool Com[maxn];
LL Num[maxn], Prim[maxn / 3];
int Cnt;

void INIT()
{
    Num[1] = 1, Num[0] = 0;
    for(LL i = 2; i <= maxn; ++i)
    {
        if(!Com[i])
        {
            Prim[Cnt++] = i;
            Num[i] = i-1;
        }
        for(LL j = 0; j < Cnt && i * Prim[j] < maxn; ++j)
        {
            Com[i*Prim[j]] = true;
            if(i % Prim[j] == 0)
            {
                Num[i*Prim[j]] = Num[i] * Prim[j];
                break;
            }
            else
                Num[i*Prim[j]] = Num[i] * (Prim[j]-1);
        }
    }
    for(LL i = 0; i < maxn; ++i) Num[i] *= Num[i];
    for(LL i = 1; i < maxn; ++i) Num[i] += Num[i-1];
}

int main()
{
    INIT();
    //cout << Num[maxn - 1] << endl;
    int t, a, b;
    scanf("%d",&t);
    for(int kase = 1; kase <= t; ++ kase)
    {
        scanf("%d%d",&a,&b);
        a = a - 1;
        printf("Case %d: %llu\n",kase, Num[b]-Num[a]);
    }
}