Description

Since $151$ is both a prime and a palindrome (it reads the same from left to right and from right to left), $151$ is a palindromic prime.

Write a program to find all palindromic primes in the range $[a, b]$ with $5 \le a < b \le 100,000,000$ (one hundred million).

Input Format

The first line contains two positive integers $a$ and $b$.

Output Format

Output a list of palindromic primes, one per line.

5 500

5
7
11
101
131
151
181
191
313
353
373
383

Hint

Hint 1: Generate palindromes and then check whether they are prime (also called “primes” or “sùshù” in pinyin).

Hint 2: Generate palindromes by combining digits properly. You might need several loops like the one below.

Problem translation from NOCOW.

USACO Training Section 1.5.

Generating palindromes of length $5$:

for (d1 = 1; d1 <= 9; d1+=2) {    // 只有奇数才会是素数
     for (d2 = 0; d2 <= 9; d2++) {
         for (d3 = 0; d3 <= 9; d3++) {
           palindrome = 10000*d1 + 1000*d2 +100*d3 + 10*d2 + d1;//(处理回文数...)
         }
     }
 }

Translated by ChatGPT 5