#include<stdio.h>
int main() {
    int youngest_age, oldest_age;
    
    if (scanf("%d %d", &youngest_age, &oldest_age) != 2) {
        printf("Invalid input\n");
        return 1;
    }
    
    if (youngest_age < 0 || oldest_age < 0 || youngest_age > oldest_age) {
        printf("Invalid input\n");
        return 0;
    }
    
    innt sum = 0;
    
    for (int i = youngest_age; i <= oldest_age; i++) {
        
        if (i % 7 == 0) {
            sum += i;
        }
    }
    
    printf("%d\n", sum);
    
    return 0;
}