import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        int p = sc.nextInt();
        int max = 0;
        TreeMap<Integer, Integer> map = new TreeMap<>();
        for (int i = 0; i < n; i++) {
            int x = sc.nextInt();
            max =  Math.max(max, x);
            int count = 0;
            while (x % p == 0) {
                x /= p;
                count++;
            }
            map.put(count, Math.max(map.getOrDefault(count, 0), x));
        }
        boolean all1 = true;
        for (int x : map.values()) {
            if (x > 1) {
                all1 = false;
                break;
            }
        }
        int limit = (m + max - 1) / max;
        if (limit <= 1) {
            System.out.println(1);
            return;
        }
        if (all1) {
            System.out.println(-1);
            return;
        }
        int ans = Integer.MAX_VALUE;
        Integer current = 0;
        TreeMap<Integer, Integer> dp = new TreeMap<>();
        dp.put(1, 0);
        while ((current = dp.higherKey(current)) != null) {
            for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
                int count = entry.getKey() + 1;
                int value = entry.getValue();
                if (value == 1) {
                    continue;
                }
                if (current * (long)value >= limit) {
                    ans = Math.min(ans, dp.get(current) + count);
                } else {
                    if (!dp.containsKey(current * value) || dp.get(current * value) > dp.get(current) + count) {
                        dp.put(current * value, dp.get(current) + count);
                    }
                }
            }
        }
        System.out.println(ans + 1);
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}