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#define ull unsigned long long
#define ll long long
#define inf 0x3f3f3f3f
#define mod (int)1e9+7
#define for0(i, n) for (int i = 0; i < n; i++)
#define for1(i, n) for (int i = 1; i <= n; i++)
#define forl(i, l, r) for (int i = l; i <= r; i++)
#define forn(i, n) for (int i = n; i >= 0; i--)
#define mem0(a) memset(a, 0, sizeof(a))
#define mem1(a) memset(a, 1 , sizeof(a))
#define mem_1(a) memset(a, -1, sizeof(a))
#define meminf(a) memset(a, inf, sizeof(a))
using namespace std;
const int N=100005;
bool a[N+1];
vector<int> prime;
void (){
memset(a,true,sizeof(a));
for(int i=2;i<=N;i++){
if(a[i]) prime.push_back(i);
for(int j=0;j<(int)prime.size()&&i*prime[j]<=N;j++){
a[i*prime[j]]=false;
if(!(i%prime[j])) break;
}
}
}
int main(){
ll t,a,b;
bool isprime[100005];
getPrime();
cin>>t;
for1(k,t){
int ans=0;
cin>>a>>b;
mem1(isprime);
for(int i=0;prime[i]*prime[i]<=b&&i<(int)prime.size();i++){
ll l=a/prime[i];
if (l*prime[i]<a) l++;
if (l<2) l=2;
for (; l*prime[i]<=b; l++) isprime[l*prime[i]-a]=0;
}
if (a==1) isprime[0]=0;
for0(i,b-a+1)
if (isprime[i])ans++;
printf("Case %d: %dn",k,ans );
}
return 0;
}
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