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