import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.Set;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		int m = Integer.parseInt(sa[1]);
		int p = Integer.parseInt(sa[2]);
		sa = br.readLine().split(" ");
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sa[i]);
		}
		br.close();

		int ans = Integer.MAX_VALUE;
		label:
		for (int i = 0; i < n; i++) {
			long x = 1;
			Set<Long> set = new HashSet<>();
			set.add(x);
			int cnt = 0;
			while (x <= m) {
				cnt++;
				x *= a[i];
				if (x > m) {
					break;
				}
				if (!set.add(x)) {
					continue label;
				}
				while (x % p == 0) {
					x /= p;
				}
			}
			ans = Math.min(ans, cnt);
		}
		if (ans == Integer.MAX_VALUE) {
			ans = -1;
		}
		System.out.println(ans);
	}
}