#include<stdio.h>
int main(){
    int lowe_bound, upper_bound;
    if(scanf("%d %d", &lower_bound, &upper_bound) != 2){
        return 1;
    }
    if(lower_bound < 0 || upper_bound < 0 || lower_bound > upper_bound){
        printf("Invalid input\n");
    }else{
        int sum = 0;
        for(int age = lower_bound; age <= upper_bound; age++){
            if(age % 7 == 0){
                sum +=age;
            }
        }
        printf("%d\n",sum);
    }
    return 0;
}