#include<stdio.h>
int main()
{
    int low ,upper,sum=0;
    scanf("%d %d",&lower,&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");
    return 0;
}