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