#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>

#define MAX 1000000

using namespace std;

vector<bool> prime(MAX + 1, true);
int a, d, n;

void sieve() {
  int i, j, limit;
  fill(prime.begin(), prime.end(), true);
  limit = (int)sqrt((double)(MAX));

  prime[1] = false;

  for(int i = 4;  i  <= MAX ; i+=2) {
    prime[i] = false;
  }

  for(int i = 3 ; i <= limit ; i += 2) {
    if(prime[i]) {
      for(int j = i ; i * j <= MAX ; j+=2) {
        prime[i * j] = false;
      }
    }
  }
}

int main() {
  sieve();

  while(cin >> a >> d >> n, a || d || n) {
    int counter = 0;

    for(int i = a ; true ; i += d) {
      if(prime[i]) {
        counter++;

        if(counter == n) {
          cout << i << endl;
          break;
        }
      }
    }
  }
}