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