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