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