/**
 *  Dirichlet's Theorem on Arithmetic Progressions (PKU 3006)
 *  by Kenji Inoue, 2006-12-30
 **/

#include <iostream>
#include <cmath>

using namespace std;

#define MAX 1000000

int main() {
  char p[MAX]; // prime table
  memset(p, 1, sizeof(p));

  p[0] = 0;
  p[1] = 0;
  for (int i=2; i<sqrt(MAX)+1; i++)
    if (p[i])
      for (int j=i*2; j<MAX; j+=i)
        p[j] = 0;

  int a, d, n;
  while (cin >> a >> d >> n, (a || d || n)) {
    int cnt = 0;
    while (1) {
      if (p[a]) cnt++;
      if (cnt == n) break;
      a += d;
    }
    cout << a << endl;
  }

  return 0;
}