#include <bits/stdc++.h>
using namespace std;

bool ish(int x) {
	vector<int> s;
	while (x > 0) {
		s.push_back(x % 10);
		x /= 10;
	}
	for (int j = s.size() - 1, i = 0; j >= 0 && i < s.size(); j--, i++)
		if (s[i] != s[j])
			return false;
	return true;
}

bool isz(int x) {
	for (int i = 3; i <= sqrt(x); i += 2)
		if (x % i == 0)
			return false;
	return true;
}

int main() {
	ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
	int a, b;
	cin >> a >> b;
	if (a > b)
		swap(a, b);
	if (a == 2)
		cout << a << endl;
	if (a % 2 == 0)
		a++;
	for (int i = a; i <= b; i += 2) {
		if (ish(i) && isz(i))
			cout << i << endl;
	}
	return 0;
}

呜呜呜，已经尽量优化了，1200ms，超得好多