import java.awt.geom.Point2D;
import java.io.*;
import java.math.BigInteger;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.Stack;
import java.util.TreeMap;
 
 
 
public class Main {
 
    static PrintWriter out = new PrintWriter(System.out);
    static FastScanner sc = new FastScanner();
    static Scanner stdIn = new Scanner(System.in);
    static boolean isPrime[];
    public static void main(String[] args) {
        makePrimeList(2 << 16);
        while(true) {
            int n = sc.nextInt();
            if(n == 0) break;
            int count = 0;
            for(int i = 2; i < n/2+1; i++) {
                if(isPrime[i] && isPrime[n-i]) {
                    count++;
                }
            }
            out.println(count);
        }
        out.flush();
         
    }
     
    public static void makePrimeList(int n) {
        boolean[] isntPrime = new boolean [n];
        isPrime = new boolean[n];
        isPrime[2] = true;
        for(int i = 3; i < n; i +=2 ) {
             
            if(!isntPrime[i]) {
                isPrime[i] = true;
                for(int j = i + i; j < n; j += i) {
                    isntPrime[j] = true;
                }
            }
        }
    }
     
     
}
//------------------------------//
//-----------//
class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
    public boolean hasNext() { skipUnprintable(); return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
     
    public int nextInt() {
         if (!hasNext()) throw new NoSuchElementException();
         int n = 0;
         boolean minus = false;
         int b = readByte();
         if (b == '-') {
             minus = true;
             b = readByte();
         }
         if (b < '0' || '9' < b) {
             throw new NumberFormatException();
         }
         while(true){
             if ('0' <= b && b <= '9') {
                 n *= 10;
                 n += b - '0';
             }else if(b == -1 || !isPrintableChar(b)){
                 return minus ? -n : n;
             }else{
                 throw new NumberFormatException();
             }
             b = readByte();
         }
    }
     
    public double nextDouble() {
        return Double.parseDouble(next());
    }
     
 
}

Measured memory_bytes: 19460