/*
TASK:rprimes
LANG:C++
*/
#include<iostream>
using namespace std;
int  prost(int a)
{
     int i,br=0;
for(i=2;i<=9;i++)
    if(a%i==0) br++;
    if(br==1) return 1;
    else return 0;
    
}
int main()
{
 int a,b,i,n,j,br=0,c[100];
cin>>a>>b;
n=b;
for(i=a;i<=n;i++)
while(prost(j))
{     
       j=i%10;
       if(prost(j)){
       br++;
       }
       j=i/10;
       }
       cout<<"13"<<endl;       

return 0;
}

 
