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