#include<bits/stdc++.h>
using namespace std;
bool book[100000001];
//用埃氏筛法生成素数表
void prime(int b) {
//初始化,默认全部都是质数
memset(book, true, sizeof(book));
book[1]=false;//1不是质数
int n=sqrt(b);
for (int i=2;i<=n;i++) {
if (book[i]) {
//质数的倍数绝对不能是倍数,把所有质数的倍数设为false
for (int j=2;j<=b/i;j++)
book[i*j]=false; //i*j<=b;
}
}
}
bool isHWS(int num) {
int temp=num,ans=0;
while (temp!=0) {
ans=ans*10+temp%10;
temp/=10;
}
if (ans==num)
return true;
else
return false;
}
int main() {
int a,b;
cin>>a>>b;
if (b>=10000000)
b=9999999;
prime(b);
if(a>b)
return 0;
if (a%2==0) a++;
for (int i=a;i<=b;i+=2) {
if (book[i] && isHWS(i))
cout<<i<<endl;
}
return 0;
}
根据数论知识中,数的整体性理论,倘若一个数是回文数且其位数为偶数,那有且仅有11,不然必定其位数是奇数。若是偶数的回文数,则必定能将11整除