---

#include <iostream>

using namespace std;

long long count_odd_sums(long long n) {
    if (n <= 0) return 0;
    
    long long count = n / 2;
    
    if (n % 2 != 0) {
        count++;
    } else {
        long long temp = n;
        int sum = 0;
        while (temp > 0) {
            sum += temp % 10;
            temp /= 10;
        }
        if (sum % 2 != 0) {
            count++;
        }
    }
    return count;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    long long a, b;
    cin >> a >> b;

    cout << count_odd_sums(b) - count_odd_sums(a - 1) << "\n";

    return 0;
}