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