#include<stdio.h>
int main()
{
    int low,high,su = 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;
}