#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);
}