#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
bool dp[5000007];
ll psum[5000007];
void PrimeSieve()
{
    dp[1]=dp[0]=true;
    ll temp=sqrt(5000007);
    for(ll i=2; i<=temp; i++)
    {
        if(!dp[i])
        {
            for(ll j=i*i; j<=5000006; j+=i) dp[j]=true;
        }
    }
}
bool isprime(ll n)
{
    if(n<2) return false;
    for(ll j=2; j<=sqrt(n); j++)
    {
        if(n%j==0) return false;
    }
    return true;
}
void psumm()
{

    for(ll i=2;i<=5000006;i++)
    {
        ll cnt=0,n=i;
        for(ll j=2;j<=sqrt(n);j++)
        {
            if(!dp[n])break;
            if(n%j==0)
            {
                while(n%j==0)
                n/=j;
                cnt+=j;
            }
        }
        if(n!=1)cnt+=n;
        if(!dp[cnt])
        psum[i]=1;
        psum[i]+=psum[i-1];
       // cout<<psum[i]<<endl;
    }
}
ll bigmod(ll base,ll power, ll mod)
{
    if(power<=0) return 1;
    ll temp=bigmod(base,power/2,mod);
    if(power%2==0) return (temp*temp)%mod;
    else return (((temp*temp)%mod)*(base%mod))%mod;
}
int main()
{
    PrimeSieve();
    psumm();
    int a,b;
    while(1)
    {
        int total=0;
        cin>>a>>b;
        if(a==0 && b==0 )break;
        total=psum[b]-psum[a-1];
        cout<<total<<endl;
    }
    return 0;
}