import java.util.*;

public class A{
	public static void main(String[] args) throws Exception{
		boolean[] isPrime = new boolean[1000000]; Arrays.fill(isPrime, true);
		isPrime[1] = false;
		for(int i = 2; i < 1000; i++)
			if(isPrime[i])
				for(int j = i * i; j < 1000000; j += i) isPrime[j] = false;
		
		Scanner sc = new Scanner(System.in);
		
		while(true){
			int a = sc.nextInt(), d = sc.nextInt(), n = sc.nextInt();
			if(a == 0) break;
			
			for(int num = 0; num < n; a += d)
				if(isPrime[a]) num++;
			
			System.out.println(a - d);
		}
	}
}