#include<cstdio>

const int N = 4e4;

int prime[N];

bool vis[N];

bool is_prime[N];

int viss[N<<];

int Prime()

{

    int cnt = ;

    for (int i = ; i <= N; ++i)

    {

        if (!vis[i])

        {

            prime[cnt++] = i;

            is_prime[i] = ;

        }

        for (int j = ; j < cnt&&i*prime[j] <= N; ++j)

        {

            vis[i*prime[j]] = ;

            if (i%prime[j] == )break;

        }

    }

    return cnt;

}

int main()

{

    int k = Prime();

    for (int i = ; i < k;++i)

    for (int j = ; j <= i; ++j)

        viss[prime[i] + prime[j]]++;

    int n;

    while (scanf("%d", &n), n)

    {

        printf("%d\n", viss[n]);

    }

}