#include<stdio.h>
int main()
{
    int lower,upper,sum = 0;
    scanf("%d",&lower);
    scanf("%d",&upper);
    if (lower < 0 || upper <0 || lower > upper)
    {
        printf("Invalid input\n");
        return 0;
    }
    for (int i  lower; i <= upper; i++)
    {
        if (i % 7 == 0){
            sum += i;''
    }
    printf("%d\n",sum);
    return 0;
}