大佬求助，最后一个点TLE

#include <cstdio>
#include <cmath>
#include <string>
using namespace std;
bool isPrime(int n) {
    if (n <= 1)
        return false;
    for (int i = 2; i <= sqrt(n); i++) {
        if (!(n % i))
            return false;
    }
    return true;
}
bool isPalindrome(int d) {
    string s = to_string(d);
    int left = 0, right = s.size() - 1;
    while (left < right) if (s[left++] != s[right--]) return false;
    return true;
}
int main() {
    int a, b;
    scanf("%d %d", &a, &b);
    for (; a <= b; a++) if (isPalindrome(a) && isPrime(a)) printf("%d\n", a);
    return 0;
}