#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

const int N = 1000 * 1000 + 100;
vector<int> primes;
bool isPrime[N];

void make_primes(){
  fill(&isPrime[0], &isPrime[N], true);
  isPrime[0] = isPrime[1] = false;
  primes.clear();
  for(int i = 2; i < N; i++){
    if(isPrime[i]){
      primes.push_back(i);
      if(i > N / i){break;}
      for(int j = i * i; j < N; j += i){
	isPrime[j] = false;
      }
    }
  }
}


int main(){
  make_primes();
  while(true){
    int a, d, n;
    cin >> a >> d >> n;
    if(a == 0 and d == 0 and n == 0){break;}
    int count = 0;
    for(int i = 0; ; i++){
      if(isPrime[a + d * i]){
	count++;
      }
      if(count == n){
	cout << a + d * i << endl;
	break;
      }
    }
  }

}