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