#include <iostream>

using namespace std;

int main()
{
    int64_t sum =0;
int a,b;
 cin>>a>>b;
  if(a%2==0)
    a++;
  if(b%2==0)
    b--;
  for(int i=a;i<=b;i+=2)
  {
      int j=i;
      while(j)
        sum+=j%10,j/=10;
  }


 cout<<sum;
}