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