#include <iostream>
#include <fstream>

using namespace std;

// 5
// 1 2 3 4 5
// 5 4 3 2 1

long sumi(long,long);
long sum_digits(long);

int main() {
	long a,b;
	cin>>a>>b;


    if(b < a) { cout<<0; return 0;}

    if (b == a && a % 2) {
        cout<<sum_digits(a);
        return 0;
    }

    if (b == a) {cout<<0; return 0;}

    cout<<sumi(a,b);



	return 0;
}
long sum_digits(long nr) {
    long S = 0;

    while(nr) {
        S += nr%10;
        nr /= 10;
    }


return S;

}
long sumi(long a, long b) {

    long S = 0;
    //par
    if (a % 2 == 0) a += 1;



    while(a <= b) {

        S += sum_digits(a);
        a += 2;
    }

    return S;
}