#include<stdio.h>
int main(){
    int a,b,c =0;
    scanf("%d %d",&a,&b);
    if(a<1 || b<1 || a<b)
    {
        printf("Invalid Input");
        return 0;
    }
    for (int i=a;i<=b;i++)
    {
        if(i%7 == 0)
        c +=i;
    }
    printf("%d",sum);
    return 0;
}