#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;
}