l,r = map(int,input().split())

ans = r-l+1
cnt = 0

chk = [0]*(r-l+1)

for i in range(l,r-1):
    for j in range(i+i,r+1,i):
        #print(j,l,"jl")
        if chk[j-l] == 0:
            chk[j-l] = 1
            cnt += 1
    #print(cnt)
#print(ans,cnt)
print(ans-cnt-1)
#print(sum(chk))