#include<stdio.h>

int calculate_sum(int lower, int upper ) {
    int sum = 0;
    for(int age = lower; age ,<= upper; age++) {
        if(age % 7 == 0) {
            sum += age;
        }
}
return sum;

int main() {
    int lower, upper;
    scanf(%d %d , &lower,&upper);

    if(lower < 0 || upper < 0 || lower > upper); {
        printf("Invalid Input\n");
    } else {
        printf("%d\n", calculate_sum(lower, upper));
    }
    return 0;
}