#include <iostream>
#include <array>
#include <algorithm>
/*
bool is_prime(unsigned int n) {
if (n == 2) {
return true;
}
if (n > 2 && n % 2) {
for (unsigned int i = 3; i < n; i++) {
if (n % i == 0) {
return false;
}
}
return true;
}
return false;
}
*/
inline bool is_palindrome(unsigned int n) {
if (n < 10) {
return true;
} else if (n > 9 && n < 100) {
return ((n / 10) == (n % 10));
} else if (n > 99 && n < 1000) {
return ((n / 100) == (n % 10));
}
return false;
}
int main()
{
std::array<unsigned int, 169> primes = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997};
std::ios_base::sync_with_stdio(0);
std::cin.tie(0);
unsigned int t;
std::cin >> t;
unsigned int nb;
for (size_t i = 0; i < t; i++) {
std::cin >> nb;
unsigned int input;
bool flag = false;
for (size_t j = 0; j < nb; j++) {
std::cin >> input;
if (!flag && std::binary_search(primes.begin(), primes.end(), input) && is_palindrome(input)) {
flag = true;
std::cout << input << std::endl;
}
}
}
return 0;
}
