686.cpp

#include <bits/stdc++.h>

using namespace std;
bool a[32770];

void prime(int n) {
    int i, j, k, l;
    memset(a, 0, sizeof(a));
    a[0] = 1;
    a[1] = 1;
    for (i = 4; i <= n; i += 2) a[i] = 1;
    for (i = 3; i * i <= n; i++) {
        if (a[i] == 0)
            for (j = i * i; j <= n; j += 2 * i) {
                a[j] = 1;
            }
    }
}

int main() {
    prime(32770);
    int i, j, k, n, count;
    while (scanf("%d", &n)) {
        if (n == 0) return 0;
        count = 0;
        for (i = 2; i <= n / 2; i++) {
            while (a[i] && i < n / 2) {
                i++;
            }
            k = n - i;
            if (!a[k]) {
                count++;
            }
        }
        printf("%d\n", count);
    }
    return 0;
}