#include<stdio.h>
int main(){
    int lower, upper;
    scanf("%d %d",&lower ,&upper);
    if (lower < 1 || upper < 1 || lower > upper) {
        printf("Invalid input");
        return 0;
    }
    int firstMultiple = ((lower + 6) / 7) * 7;
    int lastMultpile = (upper / 7) * 7;
    if(firstMultiple > lastMultpile) {
        printf("0\n");
        return 0;
    }
    int count = (lastMultiple - firstMultiple) / 7 + 1;
    int sum =  count * (firstMultiple + lastMultiple) / 2;
    printf("%d\n", sum);
    return 0;
}