using System;
class Program
{
// Function to check if a number is prime
static bool IsPrime(int n) {
if (n < 2) return false;
if (n % 2 == 0) return n == 2;
int limit = (int)Math.Sqrt(n);
for (int i = 3; i <= limit; i += 2) {
if (n % i == 0) return false;
}
return true;
}
// Function to check if all digits are unique
static bool HasUniqueDigits(int n) {
bool[] seen = new bool[10]; // track digits 0–9
while (n > 0) {
int d = n % 10;
if (seen[d]) return false; // duplicate found
seen[d] = true;
n /= 10;
}
return true;
}
static void Main()
{
for (int num = 1000; num <= 9999; num++) {
if (IsPrime(num) && HasUniqueDigits(num)) {
Console.WriteLine($"First 4-digit prime with all unique digits: {num}");
return; // stop after finding the first one
}
}
Console.WriteLine("No such number found.");
}
}
/*
run:
First 4-digit prime with all unique digits: 1039
*/
