#include <iostream>
#include <cmath>

using namespace std;

void sieve(int n, bool isprime[])
{
  isprime[0] = isprime[1] = false;
  for (int i = 2; i < n; i++) { isprime[i] = true; }

  for (int i = 2; i < (int)(sqrt((double)n) + 1); i++) {
    if (isprime[i]) {
      for (int j = i * 2; j < n; j += i) {
        isprime[j] = false;
      }
    }
  }
}

int main()
{
  int a, d, n;
  bool isprime[1048576];

  sieve(1048576, isprime);
  while (true) {
    cin >> a >> d >> n; if (a == 0 && d == 0 && n == 0) { break; }

    int c = 0;
    for (int i = a; ; i += d) {
      if (isprime[i]) {
        c++;
        if (c == n) {
          cout << i << endl;
          break;
        }
      }
    }
  }
  return 0;
}