#include 
#include 
#include 

using namespace std;


int main()
{
    double cena, pari;
    cin >> cena >> pari;
    int kolku = 0;
    for(double i = 0.0; i <= (pari - cena); i++) {
        if((int) (i + cena) % 5 == 0) {
            double procent = i / (i + cena);
            procent *= 100.0;
            if(procent > 10) break;
            if(procent >= 5 and procent <= 10) {
                kolku++;
            }
        }
    }
    cout << kolku << endl;
   return 0;
}