#include<stdio.h>
int main()
{
    int age1;
    int age2;
    int sum=0
    scanf("%d %d",&age1,&age2);
    if(age1 < 0||age2 < 0||age1>age2)
    {
        printf("Invalid input");
        return 0;
    }
    for(int i = age1;i <= age2; i++)
    {
        if(i % 7 == 0)
    sum+=i;
    }
    printf("%d",sum);
    return 0;
}