uva 10742

寫出一個質數表，然後用二分法去求跟他第一個差相對距離的數，再把答案加起來

//====================================================================||
//                                                                    ||
//                                                                    ||
//                         Author : GCA                               ||
//                  6AE7EE02212D47DAD26C32C0FE829006                  ||
//====================================================================||
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
using namespace std;
#ifdef ONLINE_JUDGE
#define ll "%lld"
#else
#define ll "%I64d"
#endif
typedef unsigned int uint;
typedef long long int Int;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\n")
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()
#define De(x)printf(#x"%d\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\
    printf("%d ",dp[htx][hty]);}Pln();}
#define M 10000005
#define PII pair<int,int>
#define PB push_back
#define oo INT_MAX
#define Set_oo 0x3f
#define Is_debug true
#define debug(...) if(Is_debug)printf("DEBUG: "),printf(__VA_ARGS__)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define eps 1e-6
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
    int tmp=min(x,y);
    return min(tmp,z);
}
int max3(int x,int y,int z){
    int tmp=max(x,y);
    return max(tmp,z);
}
int n;
bool seize[M];
vector<int> se;
void pre(){
    Set(seize,0);
    for(int i=2;i<M;i++){
        if(!seize[i]){
            se.PB(i);
            for(int j=i+i;j<M;j+=i){
                seize[j]=1;
            }
        }
    }
}
void solve(){
    int len=se.size();
    Int ans=0;
    for(int i=0;;i++){
        int k=n-se[i];
        int l=0;
        int r=len-1;
        while(r>=l){
            int mid=(r+l)>>1;
//            debug("%d",mid);

            if(se[mid]>k){
                r=mid-1;
            }else if(se[mid]<k){
                l=mid+1;
            }else{
                r=mid;
                break;
            }
        }
        if(i>=r)break;
        ans+=r-i;
    }printf("%lld\n",ans);
}
int main() {
    ios_base::sync_with_stdio(0);
    pre();
    int ff=0;
    while(~scanf("%d",&n)&&n){
        printf("Case %d: ",++ff);
        solve();
    }

















}