#include<bits/stdc++.h>
using namespace std;
int lone[10010];
int n, m, r, k, cnt = 1;
bool is_prime(int a) {
	for (int i = 2; i <= sqrt(a); i++)
		if (a % i == 0)
			return false;
	return true;
}
void var() {
	for (int i = 1; i <= n; i++)
		if (is_prime(i) && i % m == r) {
			lone[cnt] = i;
			cnt++;
		}
}
bool cmp(int a, int b) {
	return a > b;
}
int main() {
	cin >> n >> m >> r >> k;
	var();
	sort(lone + 1, lone + cnt, cmp);
	if (lone[k] == 0) {
		cout << -1;
		return 0;
	}
	cout << lone[k];
	return 0;
}

为啥是90