#include<stdio.h>
int main()
{
    int low, high, sum = 0;
    scanf("%d %d", &low, &high){
        if (low < 1 || high <1 || low > high){
            printf ("Invalid input");
            return 0;
        }
        for (int i = low; i <= high;i++)
        {
            if (i % 7 == 0)
            sum += i;
        }
        printf("%d", sum);
        return 0;
    }