#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;

       if ( age % 7 ==0){
           sum += age;
       }
       
       
       printf( "%d\n", sum );
       return 0;
 }