1259 - Goldbach's Conjecture

/***

            Bismillahir Rahmanir Rahim
            Read the name of Allah, who created you!!!
            Author : Shah Newaj Rabbi Shishir
            Department of CSE, City University, Bangladesh.

***/

#include <bits/stdc++.h>
using namespace std;

#define sf scanf
#define pf printf
#define scase sf ("%d",&tc)
#define sn sf ("%d",&n)
#define whilecase while (tc--)
#define eof while (cin >> n)
#define forloop for (pos=1; pos<=tc; pos++)
#define arrayloop (i=0; i<n; i++)
#define cinstr cin >> str
#define getstr getline (cin,str)
#define pcase pf ("Case %d: ",pos)
#define pb push_back
#define in insert
#define llu unsigned long long
#define lld long long
#define U unsigned int

const int MAX = 10000001;
bool prime[MAX];
vector <int> v;

void sieve ()
{
    int i,j;

    prime[0] = prime[1] = true;
    v.pb(2);

    for (i=4; i<MAX; i+=2)
        prime[i] = true;

    for (i=3; i*i<=MAX; i+=2)
        if (!prime[i])
            for (j=i*i; j<MAX; j+=2*i)
                prime[j] = true;

    for (i=3; i<MAX; i+=2)
        if (!prime[i])
            v.pb(i);
}

int main (void)
{
    /*freopen ("input.txt","r",stdin);
    freopen ("output.txt","w",stdout);*/
    sieve ();
    int tc,pos,n,h,i,k;

    sf ("%d",&tc);

    for (pos=1; pos<=tc; pos++)
    {
        sf ("%d",&n);

        h = n/2;
        k = 0;

        for (i=0; v[i]<=h; i++)
            if (!prime[v[i]] && !prime[n-v[i]])
                k++;

        pf ("Case %d: %d\n",pos,k);
    }

    return 0;
}