#include <stdio.h>
#define number 1000000

char prime[number];

int gcd(int n, int m) {
	if(!m) return n;
	else gcd(m, n%m);
}

void Eratosthenes(char prime[]) {
	long i, j;
	prime[1] = 1;
	for(i = 2; i < number; i++ ) {
		if(!prime[i]) {
			//printf("%d\n",i);
			for(j = 2; j*i < number; j++ ) {
				prime[i*j] = 1;
			}
		}
	}
}

int main(void) {
	int a, d, n, i, count = 0;
	Eratosthenes(prime);
	while(scanf("%d%d%d",&a,&d,&n), a+d+n) {
		count = 0;
		for(i = 0; a + i*d < number; i++ ) {
			if(!prime[a + i*d]) {
				count++;
				if(count == n) {
					printf("%d\n",a + i*d);
					break;
				}
			}
		}
	}
	return 0;
}