import java.util.Scanner;
public class Main {
    // 计算一个整数的数位之和 14=5
    public static int sum(int a) {
        int sum = 0;
        while (a / 10 != 0 || a % 10 != 0) {
            sum += a % 10;
            a = a / 10;
        }
        return sum;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 0;
        for (int i = a; i <= b; i++) {
            int sum = sum(i);
            if (sum % 5 == 0) {
                count ++;
            }
        }
        System.out.println(count);
    }
}