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