using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

using CHY72;

namespace CHY72{
    
    public class PointXY{
        public int X , Y;
        public int SQLength() { return X * X + Y * Y; }
        public bool Flag = false;
        public PointXY(int _X,int _Y) {
            X = _X; Y = _Y;
        }
        public PointXY(PointXY P1, int _X = 0, int _Y = 0) {
            X = P1.X +  _X; Y =P1.Y + _Y;
        }
        public static bool operator ==(PointXY P1, PointXY P2) {
            return (P1.X== P2.X && P1.Y == P2.Y);
        }
        public static bool operator !=(PointXY P1, PointXY P2) {return !(P1 ==P2);}
        public override int GetHashCode() {return X.GetHashCode() ^ Y.GetHashCode();}
        public override bool Equals(object obj) {
            if (obj == null || this.GetType() != obj.GetType()) {return false;}
            return (this == (PointXY)obj);
        }

    }

    public class Lib72 {
        public static int NumFromChar(char CNUM) { return CNUM - 48; }
        public static char LoopChar52(char _C, int n) {
            //Char(C#) uses Uni-Code
            //33 !  "#$%&'(  41 )
            //42 * +,-.  47/
            //48 0  .... 57 9
            //58 :;<=>? 64 @
            //65 A .... 90 Z
            //91 [\]^_ 96`
            //97 a .... 122 z
            int i_C = (int)_C;
            if (i_C > 64 && i_C < 91) i_C -= 65;//0~25 AZ
            else if (i_C > 96 && i_C < 123) i_C -= 71;//26~51 az
            else return '0';
            int RESULT = Modulo ((i_C + n ) , 52);
            if(RESULT < 26) return (char)(RESULT+65);
            else return (char)(RESULT + 71);
        }
        public static int Modulo(int A, int B)  {
            // -6 % 5 == -1
            // -6 % 5 == 4
            int Result = A % B;
            if (Result >= 0) { return Result; }
            else return Result + B;
        }
        public static int intFromHourMinSec(int _h,int _m,int _s) {
            return _s + 60 * _m + 3600 * _h;
        }

        public static int[] KETAArray(int Num) {return KETAArray(Num.ToString()); }
        public static int[] KETAArray(string Num) {
            char[] cKETA = Num.ToCharArray();
            int[] iKETA = new int[cKETA.Length];
            for (int i = 0; i < iKETA.Length; i++) {
                iKETA[i] = NumFromChar(cKETA[i]);
            }
            return iKETA;
        }
        public static int KETA(int Num) { return Num.ToString().ToCharArray().Length; }
        public static int FromKETAArray(int[] _ketaarray) {
            int result = 0;
            int[] R_ketaarray = _ketaarray.Reverse().ToArray(); 
            for (int i = 0,j=1; i < R_ketaarray.Length; i++,j *=10) {
                result += j * R_ketaarray[i];
            }
            return result;
        }
        public static bool isPrime(int p) {
            if (p != 2 && p % 2 == 0) return false;
            if (p == 1) return false;
            int SQp = (int)(Math.Sqrt(p));
            for (int i = 3; i <= SQp; i++) {
                if (p % i == 0) return false;
            }
            return true;
        } 
    }
}    

public class Program {
    static bool ReadLine_1(ref int num1, bool Fin0 = true) {
        string str = Console.ReadLine();
        num1 = int.Parse(str);
        return (Fin0 && num1 == 0);
    }
    static int  ReadLine_1() {
        return  int.Parse(Console.ReadLine());
    }
    static bool ReadLine_2(ref int num1, ref int num2, char Spliter = ' ', bool Fin0 = true,int FinNum =0) {
        string str = Console.ReadLine();
        num1 = int.Parse(str.Split(Spliter)[0]);
        num2 = int.Parse(str.Split(Spliter)[1]);
        return (Fin0 && num1 == FinNum && num2 == FinNum);
    }
    static int[] ReadLine_Array(char Spliter = ' ') {
        return Console.ReadLine().Split(Spliter).Select(s => int.Parse(s)).ToArray();
    }

    const int DefaultMax = 72727272;
    
    

    static int NextX(int A, int B, int C, int X) {
        return ((A * X + B) % C);
    }

    static void Main(string[] args) {
        while (true) {
            int[] NABCX = ReadLine_Array();
            if (NABCX.Sum()== 0) return;
            int[] Require = ReadLine_Array();
            Queue<int> Q = new Queue<int>();
            for (int i = 0; i < NABCX[0];i ++ ) {
                Q.Enqueue (Require [i]);
            }
            int X = NABCX [4];
            int result = DefaultMax;
            for (int i = 0; i < 10001; i++) {
                if(X == Q.Peek ()){
                    Q.Dequeue();
                    if (Q.Count == 0) { result = i; break; }
                }
                X = NextX(NABCX[1], NABCX[2],NABCX[3],X);
            }
            if (result == DefaultMax) Console.WriteLine("-1");
            else Console.WriteLine(result );
        }
    }
}

Measured memory_bytes: 6404