#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>


void Sieve(int n, int *isprime)
{
  int i,p;
  for(i=0;i<=n;i++) if(i%2==0) isprime[i]=0;else isprime[i]=1;
  isprime[1]=0;isprime[2]=1;
  for(i=3;i<=(int)sqrt((double)n);i+=2){
    if(isprime[i]){
      for(p=i*i;p<=n;p+=2*i)isprime[p]=0;
    }
  }
}
		   
main()
{
  int prime[1000000];
  Sieve(1000000,prime);

  while(1){
    int a,d,n;
    int i,count=0,tmp;
    scanf("%d %d %d",&a,&d,&n);
    if(a+d+n ==0)break;
    for(i=0;;i++){
      tmp = a+d*i;
      if(prime[tmp])count++;
      if(count == n) break;
    }
    printf("%d\n",tmp);
  }
  return 0;
}