#include<stdio.h>
int main ()
{
    int low,high;
    scanf("%d %d",&low,&high);
    for (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;
}