#include <stdio.h>
int main() {
    int lower,upper,sum = 0;
    scanf('%d',&lower);
    scanf('%d',&upper);
    if (lower < 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;
}