#include<stdio.h>

int main() {
    int lower_age,upper_age;
    scanf("%d%d",&lower_age,&upper_age);
    if(lower_age<0||upper_age<0||lower_age>upper_age) {
        printf("Invalid input\n");
    }
    else{
        int sum=0;
        for(int i=lower_age;i<=upper_age;i++){
            if(i%7==0){
                sum +=i;
            }
        }
        printf("%d\n",sum)
    }
    return 0;
}