#include <iostream>

 #include <cstring>

 #include <cmath>

 #include <cctype>

 #include <cstdio>

 #include <cmath>

 #include <algorithm>

 #include <numeric>

 using namespace std;

 const int N = , M = ;

 bool is[N]; int prm[M];

 int getprm (int n) {

     int i, j, k = ;

     int s, e = (int)(sqrt (0.0 + n) + );

     memset (is, , sizeof(is));

     prm[k ++] = ; is[] = is[] = ;

     for (i = ; i < n; i += ) is[i] = ;

     for (i = ; i < e; i += ) {

         if (is[i]) {

             prm[k ++] = i;

             for (s = i * , j = i * i; j < n; j += s) {

                 is[j] = ;

             }

         }

     }

     for (; i < n; i += ) {

         if (is[i]) prm[k ++] = i;

     }

     return k;

 }

 int main () {

     ios :: sync_with_stdio(false);

     //freopen("out.txt", "w", stdout);

     getprm();

     /*for (int i = 0 ; i < 78499; ++ i) {

         cout << i  << " : " << prm[i] << endl;

     }*/

     long long a, d, n;

     long long cnt = , cur = ;

     while (cin >> a >> d >> n) {

         if (a ==  && d ==  && n == ) break;

         cnt =  ;

         while () {

             if (binary_search(prm, prm + , a)) {

                 cnt ++;

                 if (cnt == n) break;

             }

             a += d;

             //cout << "step: " << cnt << " " << a << endl;

         }

         cout << a << endl;

     }

     return ;

 }