#include <cstdio>

using namespace std;

bool pm[1000002];

bool usd[1000002];

bool judge(int x)

{

    if(usd[x])return pm[x];

    usd[x] = true;

    if(x == 2) return pm[x] = true;

    if(((x & 1) == 0) || (x < 2))return pm[x] = false;

    for(int i = 3;i * i <= x;i+= 2)

    {

        if(x % i == 0)return pm[x] = false;

    }

    return pm[x] = true;

}

int main(){

    int a,d,n;

    while(scanf("%d%d%d",&a,&d,&n) == 3 && a)

    {

        int cnt = 0;

        for(int tn = 0;tn < n;cnt++)

        {

            if(judge(cnt * d + a))tn++;

            if(tn == n)break;

        }

        printf("%d\n",cnt * d + a);

    }

    return 0;

}