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