l,r=map(int,input().split())
x=[i for i in range(l,r+1)]
y=[1]*len(x)
z=max(2,int(l**0.5))
while z**2<=r:
    if z**2>=l:
        y[z**2-l]=0
    z+=1
for i in range(2,10**6):
    v=i**2
    z=(v-l%v)%v
    for j in range(z,len(x),v):
        y[j]=0
print(sum(y))