import java.util.ArrayList;
import java.util.List;
public class PrimeConcat {
// Function to check primality
public static boolean isPrime(long n) {
if (n < 2) return false;
if (n % 2 == 0 && n != 2) return false;
for (long i = 3; i * i <= n; i += 2) {
if (n % i == 0) return false;
}
return true;
}
// Concatenate two integers
public static long concat(int a, int b) {
String s = String.valueOf(a) + String.valueOf(b);
return Long.parseLong(s);
}
public static void main(String[] args) {
int limit = 12; // you can increase this
List<Integer> primes = new ArrayList<>();
// Generate primes up to limit
for (int i = 2; i <= limit; i++) {
if (isPrime(i)) {
primes.add(i);
}
}
// Check pairs
for (int i = 0; i < primes.size(); i++) {
for (int j = 0; j < primes.size(); j++) {
if (i == j) continue; // skip same prime if you want
long num = concat(primes.get(i), primes.get(j));
if (isPrime(num)) {
System.out.println(primes.get(i) + " + " + primes.get(j)
+ " -> " + num + " is prime");
}
}
}
}
}
/*
run:
2 + 3 -> 23 is prime
2 + 11 -> 211 is prime
3 + 7 -> 37 is prime
3 + 11 -> 311 is prime
5 + 3 -> 53 is prime
7 + 3 -> 73 is prime
11 + 3 -> 113 is prim
*/
