1 #include<algorithm>
 2 #include<iostream>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<vector>
 7 #include<map>
 8 #include<set>
 9 using std::cin;
10 using std::cout;
11 using std::endl;
12 using std::find;
13 using std::sort;
14 using std::set;
15 using std::map;
16 using std::pair;
17 using std::vector;
18 using std::lower_bound;
19 #define sz(c) (int)(c).size()
20 #define all(c) (c).begin(), (c).end()
21 #define iter(c) __typeof((c).begin())
22 #define cls(arr,val) memset(arr,val,sizeof(arr))
23 #define cpresent(c, e) (find(all(c), (e)) != (c).end())
24 #define rep(i, n) for (int i = 0; i < (int)(n); i++)
25 #define tr(c, i) for (iter(c) i = (c).begin(); i != (c).end(); ++i)
26 #define pb(e) push_back(e)
27 #define mp(a, b) make_pair(a, b)
28 const int Max_N = 10010;
29 typedef unsigned long long ull;
30 struct PrimeSpilt {
31     int tot, prime[Max_N];
32     inline bool isPrime(int n) {
33         for(int i = 2; i * i <= n; i++) {
34             if(!(n % i)) return false;
35         }
36         return n != 1;
37     }
38     inline void init() {
39         tot = 0;
40         for(int i = 1;i < Max_N ;i++) {
41             if(isPrime(i)) prime[tot++] = i;
42         }
43     }
44     inline void work(int n) {
45         int ans = 0;
46         for(int i = 0;i < tot && prime[i] < n; i++) {
47             int p = lower_bound(prime + i, prime + tot, n - prime[i]) - prime;
48             if(prime[i] + prime[p] == n && i != p) ans++;
49         }
50         printf("%d\n", ans);
51     }
52 }go;
53 int main() {
54 #ifdef LOCAL
55     freopen("in.txt","r",stdin);
56     freopen("out.txt","w+",stdout);
57 #endif
58     int n;
59     go.init();
60     while(~scanf("%d", &n) && n) go.work(n);
61     return 0;
62 }