#include<stdio.h>
int lower_bound,upper_bound;
scanf("%d %d",&lower_bound,&upper_bound);
if(lower_bound<0 || upper_bound<0 ||lower_bound>upper_bound){
    return 1;
}
int sum_of_ages=0;
for(int age = lower_bound;age<=upper_bound;age++){
    if(age % 7==0){
        sum_of_ages += age;
    }
}
printf("%d\n",sum_of_ages);
return 0;
}