#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");
        return0;
    }
}for (int i=lower; i<=upper;i++){ 
    if(i%7==0){
        sum+=i;
    }
    }
    printf("%d\n",sum);
    return 0;
    }