#include<stdio.h>
int main()
{
    int lower, uper,sum = 0;
    scanf("%d",&lower);
    scanf("%d",&upper);
    if(lower < 0 || upper < 0 || lower > upper){
        printf("Inalid input\n");
        return 0;
    }
    for(int i = lower; i <= upper; i++){
        if (i % 7 == 0){
            sum += i;
        }
    }
    printf("%d\n",sum);
    return 0;
}