// editor3
#include<stdio.h>
int main()
{
    int youngest_age, oldest_age;
    int sum=0;
    if(scanf("%d%d",&youngest_age, &oldest_age) != 2)
    {
        printf("Invalid input\n");
        return 1;
    }
    if(youngest_age < 0 || oldest_age < 0 || youngest_age > oldest_age)
    {
        printf("Invalid input\n");
    }
    else
    {
        for(int age = ypungest_age; age <= oldest_age; age++)
        {
            if(age%7 == 0)
            {
                sum += age;
            }
        }
        printf("%d\n",sum);
    }
    return 0;
}