x,y = map(int, input().split())
count =0
sum=0
for i in range(x,y+1):
    list1 =list(str(i))
    for j in list1:
        count+=int(j)
    if(count%5==0):
        sum+=1
        count =0
    else:
        count =0
    list1.clear()
print(sum)