#include <iostream>

using namespace std;

bool nprimes[1000001];

int main(){
	memset(nprimes,0,sizeof(nprimes));
	nprimes[1] = true;
	for(int i=2;i<=1000000;i++){
		if(!nprimes[i]){
			for(int j=2;i*j<=1000000;j++){
				nprimes[i*j] = true;
			}
		}
	}
	
	int a,d,n;
	while(cin>>a>>d>>n,a||d||n){
		int idx = 0;
		int t = a;
		while(1){
			if(!nprimes[t])
				idx++;			
			if(idx==n) break;
			t += d;
		}
		cout << t << endl;
	}
}