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