#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF (1<<29)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!\n");
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
#define IN(n) int n;scanf("%d",&n);
#define FOR(i, m, n) for (int i(m); i < n; i++)
#define REP(i, n) FOR(i, 0, n)
#define F(n) REP(i, n)
#define FF(n) REP(j, n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
void ga(int N,int *A){F(N)scanf("%d",A+i);}
#define MX (10000009)
#define IS(A) ((cn[A>>6]>>(A&63))&1)
#define ST(A) (cn[A>>6]|=1ULL<<((A&63)))
ll cn[1+(MX>>6)];
int P[MX>>1]={2},L=1;
void gen(){
    ST(0),ST(1);
    int Q(1+sqrt(MX));
    for(ll i(4);i<MX;i+=2)ST(i);
    for(int k(3);k<=Q;k+=2)if(!IS(k))
        for(ll h(k<<1),j(k*k);j<MX;j+=h)ST(j);
    for(int i(3);i<MX;i+=2)if(!IS(i))P[L++]=i;
}
ll sm(int N){
    ll S=0,p=upper_bound(P-1,P+L,N)-P-1;
    FT(1,L&&P[k]<N){
        while(p>0&&P[k]+P[p]>N)--p;
        S+=p-(p>=k);
    }
    return S>>1;
}
int B,E;
int main(void){
    gen();
    while(scanf("%d%d",&B,&E),B|E)printf("%lld\n",sm(E/2*2)-sm(--B/2*2));
    return 0;
}