using System;
using System.Linq;

class B
{
	static int[] Read() => Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
	static (int, int) Read2() { var a = Read(); return (a[0], a[1]); }
	static (int, int, int) Read3() { var a = Read(); return (a[0], a[1], a[2]); }
	static long[] ReadL() => Array.ConvertAll(Console.ReadLine().Split(), long.Parse);
	static void Main()
	{
		var (n, m, p) = Read3();
		var a = ReadL();

		a = a.Where(x => Gcd(x, p) == 1).ToArray();
		if (!a.Any()) { Console.WriteLine(-1); return; }
		var amax = a.Max();

		long x = 1;
		for (int i = 1; ; i++)
		{
			x *= amax;
			if (x > m)
			{
				Console.WriteLine(i);
				return;
			}
		}
	}

	static long Gcd(long a, long b) { for (long r; (r = a % b) > 0; a = b, b = r) ; return b; }
}