#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;
}