#include <bits/stdc++.h>

using namespace std;

int main()
{
    long long a, b;
    scanf("%lld %lld", &a, &b);
    if (a % 2 == 0)
        ++a;
    if (b % 2 == 0)
        --b;
    long long s = 0, ss, x;
    for (; a <= b; a += 2) {
        ss = 0;
        x = a;
        while (x) {
            ss += x % 10;
            x /= 10;
        }
        s += ss;
    }
    printf("%lld", s);
    return 0;
}