Matha Nosto

#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define maxSz 10000007
int mark[maxSz];
vector<int> vec;
vector<int>::iterator it1,it2;
void sieve(int n)
{
    int cnt=0;
    mark[1]=1;
    mark[2]=0;
    for(int i=4;i<=n;i+=2)mark[i]=1;
    for(int i=3;i*i<=n;i+=2)
    {
        if(!mark[i])
        {
            for(int j=i*i;j<=n;j+=i*2)
            {
                mark[j]=1;
            }
        }
    }
    for(int i=1;i<=maxSz;i++)if(!mark[i])vec.push_back(i);

    return;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    #ifndef ONLINE_JUDGE
    freopen("input.cpp","r",stdin);
    //freopen("output.cpp","w",stdout);
    #endif // ONLINE_JUDGE
    sieve(maxSz);
    int a,b;
    while(cin>>a>>b && a!=0 && b!=0)
    {
        int cnt=0;
        if(a%2==1)a++;
        if(b%2==1)b--;
        for(int i=a;i<=b;i+=2)
        {
            it1=upper_bound(vec.begin(),vec.end(),i);
            int in=distance(vec.begin(),it1)-1;
            for(int j=0,k=in;j<in/2 && k>in/2;j++,k--)if(vec[j]+vec[k]==i)cnt++;
        }
        cout<<cnt<<endl;
    }
    return 0;
}