#include<iostream>
#include<cstdio>
using namespace std;
int prime[187]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,
89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,
223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,
337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,
457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,
593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,
719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,
857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,
997,1009,1013,1019,1021,1031,1033,1039,1049,1051,1061,1063,1069,1087,1091,1093,
1097,1103,1109,1117};
int main()
{
    int a,b,n;
    while(scanf("%d %d %d",&a,&b,&n)!=EOF)
    {
        if(a==0&&b==0&&n==0)    break;
        int i=0;
        while(true)
        {
            if(a==1)    a+=b;
            int t=0;
            for(int j=0;j<187;j++)
            {
                if(a==prime[j])
                {
                    i++;
                    break;
                }
                else if(a%prime[j])
                {
                    t++;
                }
            }
            if(t==187)  i++;

            if(i==n)    break;
            a+=b;
        }
        printf("%d\n",a);
    }
    return 0;
}