#include<stdio.h>
int main(){
    int lower,upper,sum = 0;
    scanf("%d",&lower);
    scanf("%d",&upper);
    if (lower < 0 || uooer < 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;
}