1 #include<bits/stdc++.h>
2 #define maxn 9999999
3 using namespace std;
4 bool prime1[maxn];
5 int cnt,a,b,num;
6 bool prime2(int n)
7 {
8 int sum=0,tmp=n;
9 while(tmp){
10 sum=sum*10+tmp%10;
11 tmp/=10;
12 }
13 if(sum==n)return true;
14 else return false;
15 }
16 int main()
17 {
18 memset(prime1,true,sizeof(prime1));
19 prime1[0]=prime1[1]=false;
20 for(int i=4;i<maxn;i+=2)prime1[i]=false;
21 for(int i=3;i<=3163;i+=2){
22 if(prime1[i]){
23 for(int j=i*i;j<maxn;j+=2*i)prime1[j]=false;
24 }
25 }
26 while(cin>>a>>b){
27 num=0;
28 for(int i=a;i<=b;i++){
29 if(i>=maxn)continue;
30 if(prime1[i]&&prime2(i))num++;
31 }
32 cout<<num<<endl;
33 }
34 return 0;
35 }