import sys
readline=sys.stdin.readline

def Primes_Count(N):
    if N<2:
        return 0
    v=int(N**0.5)+1
    smalls=[i//2 for i in range(1,v+1)]
    smalls[1]=0
    s=v//2
    roughs=[2*i+1 for i in range(s)]
    larges=[(N//(2*i+1)+1)//2 for i in range(s)]
    skip=[False]*v
    pc=0
    for p in range(3,v):
        if smalls[p]<=smalls[p-1]:
            continue
        q=p*p
        pc+=1
        if q*q>N:
            break
        skip[p]=True
        for i in range(q,v,2*p):
            skip[i]=True
        ns=0
        for k in range(s):
            i=roughs[k]
            if skip[i]:
                continue
            d=i*p
            larges[ns]=larges[k]-(larges[smalls[d]-pc] if d<v else smalls[N//d])+pc
            roughs[ns]=i
            ns+=1
        s=ns
        for j in range((v-1)//p,p-1,-1):
            c=smalls[j]-pc
            e=min((j+1)*p,v)
            for i in range(j*p,e):
                smalls[i]-=c
    for k in range(1,s):
        m=N//roughs[k]
        s=larges[k]-(pc+k-1)
        for l in range(1,k):
            p=roughs[l]
            if p*p>m:
                break
            s-=smalls[m//p]-(pc+l-1)
        larges[0]-=s
    return larges[0]

L,R=map(int,readline().split())
ans=Primes_Count(R)-Primes_Count(L-1)+Primes_Count(2*R-1)-Primes_Count(2*L)
if R==1:
    ans+=1
print(ans)