#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;
}