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