#include<stdio.h>
int mian()
{
    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;
}