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