def Odd():
    sum = 0
    a,b = map(int, input().split())
    if a%2==0:
        a+=1
    if b%2!=0:
        b+=1
    for i in range(a,b,2):
        n,r = i,0
        while n:
            r, n = r + n % 10, n // 10
        sum += r
    print(sum)

Odd()