using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Threading;
using static System.Math;
namespace CpLibrary.Contest
{
	public class SolverB : SolverBase
	{
		Scanner sr;
		bool isMultipleTestcases = false;

		public override void Solve()
		{
			var (n, m, p) = sr.ReadValue<int, long, long>();
			var a = sr.ReadLongArray(n);
			var c = Enumerable.Repeat(1, n).ToArray();
			for (int i = 0; i < n; i++)
			{
				while (a[i] % p == 0)
				{
					c[i]++;
					a[i] /= p;
				}
			}
			var ans = long.MaxValue;
			for (int i = 0; i < n; i++)
			{
				if (a[i] == 1) continue;
				var count = (int)Log(m, a[i]) - 1;
				var t = Pow(a[i], count);
				while (t <= m)
				{
					t *= a[i];
					count++;
				}
				ans.Chmin(count * c[i] - (c[i] - 1));
			}
			Console.WriteLine(ans == long.MaxValue ? -1 : ans);
		}

		public static long Pow(long x, long pow)
		{
			long ret = 1;
			for (int i = 1; i <= pow; i *= 2, x *= x)
			{
				if ((pow / i) % 2 == 1) ret *= x;
			}
			return ret;
		}

		public SolverB(Scanner sr) => this.sr = sr;

		public override void Run()
		{
			var _t = 1;
			if (isMultipleTestcases) _t = sr.ReadInt();
			while (_t-- > 0) Solve();
		}
	}

	public static class ProgramB
	{
		public static void Main(string[] args)
		{
			var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
			Console.SetOut(sw);
			var sr = new Scanner(new StreamReader(Console.OpenStandardInput()));
			var solver = new SolverB(sr);
			var thread = new Thread(new ThreadStart(() => solver.Run()), 1 << 27);
			thread.Start();
			thread.Join();
			Console.Out.Flush();
		}

		public static void Expand() => SourceExpander.Expander.Expand();
	}
}
#region Expanded by https://github.com/naminodarie/SourceExpander
namespace CpLibrary { public static class Extention { public static string Join<T>(this IEnumerable<T> x, string separator = "") => string.Join(separator, x); public static string Join<T>(this IEnumerable<T> x, char separator) => string.Join(separator, x); public static int UpperBound<T>(this IList<T> list, T value) => list.BinarySearch(value, true, 0, list.Count, Comparer<T>.Default); public static int LowerBound<T>(this IList<T> list, T value) => list.BinarySearch(value, false, 0, list.Count, Comparer<T>.Default); public static int BinarySearch<T>(this IList<T> list, T value, bool isUpperBound, int index, int length, Comparer<T> comparer) { var ng = index - 1; var ok = index + length; while (ok - ng > 1) { var mid = ng + (ok - ng) / 2; var res = comparer.Compare(list[mid], value); if (res < 0 || (isUpperBound && res == 0)) ng = mid; else ok = mid; }  return ok; }  public static bool Chmax<T>(ref this T a, T b) where T : struct, IComparable<T> { if (a.CompareTo(b) >= 0) return false; a = b; return true; }  public static bool Chmin<T>(ref this T a, T b) where T : struct, IComparable<T> { if (a.CompareTo(b) <= 0) return false; a = b; return true; } } }
namespace CpLibrary { public class Scanner { public StreamReader sr { get; private set; }  string[] str; int index; char[] separators; public Scanner(StreamReader sr, char[] separators) { this.sr = sr; this.separators = separators; str = new string[0]; index = 0; }  public Scanner(StreamReader sr): this(sr, new char[]{' '}) { }  public Scanner(): this(new StreamReader(Console.OpenStandardInput()), new char[]{' '}) { }  public string Read() { if (index < str.Length) return str[index++]; string s; do s = sr.ReadLine(); while (s == ""); str = s.Split(separators, StringSplitOptions.RemoveEmptyEntries); index = 0; return str[index++]; }  public string ReadString() => Read(); public string[] ReadStringArray(int n) { var arr = new string[n]; for (int i = 0; i < n; i++) { arr[i] = ReadString(); }  return arr; }  public int ReadInt() => int.Parse(ReadString()); public int[] ReadIntArray(int n) => ReadValueArray<int>(n); public long ReadLong() => long.Parse(ReadString()); public long[] ReadLongArray(int n) => ReadValueArray<long>(n); public double ReadDouble() => double.Parse(ReadString()); public double[] ReadDoubleArray(int n) => ReadValueArray<double>(n); public BigInteger ReadBigInteger() => BigInteger.Parse(ReadString()); public T1 ReadValue<T1>() => (T1)Convert.ChangeType(ReadString(), typeof(T1)); public T1[] ReadValueArray<T1>(int n) { var arr = new T1[n]; for (int i = 0; i < n; i++) { arr[i] = ReadValue<T1>(); }  return arr; }  public (T1, T2) ReadValue<T1, T2>() => (ReadValue<T1>(), ReadValue<T2>()); public (T1, T2, T3) ReadValue<T1, T2, T3>() => (ReadValue<T1>(), ReadValue<T2>(), ReadValue<T3>()); public (T1, T2, T3, T4) ReadValue<T1, T2, T3, T4>() => (ReadValue<T1>(), ReadValue<T2>(), ReadValue<T3>(), ReadValue<T4>()); public (T1, T2, T3, T4, T5) ReadValue<T1, T2, T3, T4, T5>() => (ReadValue<T1>(), ReadValue<T2>(), ReadValue<T3>(), ReadValue<T4>(), ReadValue<T5>()); public (T1, T2, T3, T4, T5, T6) ReadValue<T1, T2, T3, T4, T5, T6>() => (ReadValue<T1>(), ReadValue<T2>(), ReadValue<T3>(), ReadValue<T4>(), ReadValue<T5>(), ReadValue<T6>()); public (T1, T2, T3, T4, T5, T6, T7) ReadValue<T1, T2, T3, T4, T5, T6, T7>() => (ReadValue<T1>(), ReadValue<T2>(), ReadValue<T3>(), ReadValue<T4>(), ReadValue<T5>(), ReadValue<T6>(), ReadValue<T7>()); public (T1[], T2[]) ReadValueArray<T1, T2>(int n) { var(v1, v2) = (new T1[n], new T2[n]); for (int i = 0; i < n; i++) { (v1[i], v2[i]) = ReadValue<T1, T2>(); }  return (v1, v2); }  public (T1[], T2[], T3[]) ReadValueArray<T1, T2, T3>(int n) { var(v1, v2, v3) = (new T1[n], new T2[n], new T3[n]); for (int i = 0; i < n; i++) { (v1[i], v2[i], v3[i]) = ReadValue<T1, T2, T3>(); }  return (v1, v2, v3); }  public (T1[], T2[], T3[], T4[]) ReadValueArray<T1, T2, T3, T4>(int n) { var(v1, v2, v3, v4) = (new T1[n], new T2[n], new T3[n], new T4[n]); for (int i = 0; i < n; i++) { (v1[i], v2[i], v3[i], v4[i]) = ReadValue<T1, T2, T3, T4>(); }  return (v1, v2, v3, v4); }  public (T1[], T2[], T3[], T4[], T5[]) ReadValueArray<T1, T2, T3, T4, T5>(int n) { var(v1, v2, v3, v4, v5) = (new T1[n], new T2[n], new T3[n], new T4[n], new T5[n]); for (int i = 0; i < n; i++) { (v1[i], v2[i], v3[i], v4[i], v5[i]) = ReadValue<T1, T2, T3, T4, T5>(); }  return (v1, v2, v3, v4, v5); }  public (T1[], T2[], T3[], T4[], T5[], T6[]) ReadValueArray<T1, T2, T3, T4, T5, T6>(int n) { var(v1, v2, v3, v4, v5, v6) = (new T1[n], new T2[n], new T3[n], new T4[n], new T5[n], new T6[n]); for (int i = 0; i < n; i++) { (v1[i], v2[i], v3[i], v4[i], v5[i], v6[i]) = ReadValue<T1, T2, T3, T4, T5, T6>(); }  return (v1, v2, v3, v4, v5, v6); }  public (T1[], T2[], T3[], T4[], T5[], T6[], T7[]) ReadValueArray<T1, T2, T3, T4, T5, T6, T7>(int n) { var(v1, v2, v3, v4, v5, v6, v7) = (new T1[n], new T2[n], new T3[n], new T4[n], new T5[n], new T6[n], new T7[n]); for (int i = 0; i < n; i++) { (v1[i], v2[i], v3[i], v4[i], v5[i], v6[i], v7[i]) = ReadValue<T1, T2, T3, T4, T5, T6, T7>(); }  return (v1, v2, v3, v4, v5, v6, v7); } } }
namespace CpLibrary { public interface ISolver { public void Solve(); public void Run(); }  public abstract class SolverBase : ISolver { public abstract void Solve(); public abstract void Run(); public bool YesNo(bool condition) { Console.WriteLine(condition ? "Yes" : "No"); return condition; }  public bool YESNO(bool condition) { Console.WriteLine(condition ? "YES" : "NO"); return condition; }  public bool yesno(bool condition) { Console.WriteLine(condition ? "yes" : "no"); return condition; } } }
namespace SourceExpander{public class Expander{[Conditional("EXP")]public static void Expand(string inputFilePath=null,string outputFilePath=null,bool ignoreAnyError=true){}public static string ExpandString(string inputFilePath=null,bool ignoreAnyError=true){return "";}}}
#endregion Expanded by https://github.com/naminodarie/SourceExpander