using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Diagnostics;
static class Program{
	const long inf=long.MaxValue>>1;
	const int mod=998244353;
	static Sc sc=new Sc();
	static void Main(){
		Pt pt=new Pt(Solve);
		pt.Sm();
	}
	static void Solve(Pt pt) {
		var (h,w,n,p)=sc.Tp4<int>();
		var a = new int[n][];
		for(int i = 0;i<n;i++) {
			a[i] = sc.Ia;
		}
		a=a.OrderBy(x => x[0]).ThenBy(x => x[1]).ToArray();
		St st = new St(w+1,true,false,0);
		for(int i = 0;i<n;i++) {
			var e = st.Get(0,a[i][1]).d;
			st.Ud(a[i][1],e+1);
		}
		var g =st.Get(0,w).d;
		Mint t1 = 1;
		Mint t2 = 2;
		t1/=p;
		t2/=p;
		pt.Wl(1-(Mint)(Fp((long)(1-t2),g)*Fp((long)(1-t1),h+w-3-g)));
	}
	static long Fp(long x,long e) {
		long r = 1;
		while(e>0) {
			if((e&1)>0) { r*=x; r%=mod; }
			x=x*x%mod;
			e>>=1;
		}
		return r;
	}
}
public struct Mint {
	const int mod = 998244353;
	private long d;
	public Mint(long d) { this.d=d; }
	public static implicit operator Mint(long d) { return new Mint(d%mod); }
	public static explicit operator long(Mint d) { return d.d; }
	public override string ToString() { return d.ToString(); }
	public static Mint operator +(Mint a,long b) { a.d=(mod+a.d+b%mod)%mod; return a; }
	public static Mint operator +(Mint a,Mint b) { a.d=(a.d+b.d)%mod; return a; }
	public static Mint operator -(Mint a,long b) { a.d=(mod+a.d-b%mod)%mod; return a; }
	public static Mint operator -(Mint a,Mint b) { a.d=(mod+a.d-b.d)%mod; return a; }
	public static Mint operator *(Mint a,long b) { a.d=b%mod*a.d%mod; return a; }
	public static Mint operator *(Mint a,Mint b) { a.d=a.d*b.d%mod; return a; }
	public static Mint operator /(Mint a,long b) { a.d=a.d*Mi(b)%mod; return a; }
	public static Mint operator /(Mint a,Mint b) { a.d=a.d*Mi(b.d)%mod; return a; }
	public static bool operator ==(Mint a,long b) { return (long)a==b; }
	public static bool operator !=(Mint a,long b) { return (long)a!=b; }
	public override bool Equals(object obj) { return false; }
	public override int GetHashCode() { return 0; }
	public static long Mi(long a) {
		a=(a+mod)%mod;
		long b = mod, u = 1, v = 0;
		while(b>0) {
			long t = a/b;
			a-=t*b; (a, b)=(b, a);
			u-=t*v; (u, v)=(v, u);
		}
		u%=mod;
		if(u<0) { u+=mod; }
		return u%mod;
	}
}
public class St {
	public class Dt {
		public int n;
		public long d;
		public Dt(long d,int n) { this.d=d; this.n=n; }
		public override string ToString() => "n:"+n.ToString()+" d:"+d.ToString();
	}
	private Dt[] dat;
	private int n, cnt;
	private bool ku;
	private Dt du;
	private Func<Dt,Dt,Dt> compare;
	public St(int n,bool mm,bool ku,long df) {
		this.n=n;
		this.ku=ku;
		if(mm) { du=new Dt(long.MinValue,-1); compare=CoMax; }
		else { du=new Dt(long.MaxValue,-1); compare=CoMin; }
		cnt=n<<1;
		dat=new Dt[cnt];
		for(int i = cnt-1;i>=cnt-n;i--) { dat[i]=new Dt(df,n-cnt+i); }
		for(int i = cnt-n-1;i>0;i--) { dat[i]=dat[i<<1]; }
	}
	private Dt CoMax(Dt x,Dt y) { return x.d>y.d ? x : y; }
	private Dt CoMin(Dt x,Dt y) { return x.d<y.d ? x : y; }
	public void Ud(int q,long b) {
		q+=n;
		if(ku) { dat[q].d+=b; }
		else { dat[q].d=b; }
		while(q>1) { dat[q>>=1]=compare(dat[q<<1],dat[(q<<1)+1]); }
	}
	public Dt Get(int l,int r) {
		Dt x = du;
		l+=n; r+=n;
		while(l<=r) {
			if((l&1)==1) { x=compare(x,dat[l]); l++; }
			if((r&1)==0) { x=compare(x,dat[r]); r--; }
			l>>=1; r>>=1;
		}
		return x;
	}
	public (int r, long d) Bsl(int l,long b) {
		Dt x = du, bd = new Dt(b,-1);
		int r = cnt-1;
		l+=n;
		var sk = new Stack<int>();
		while(l<=r) {
			if((l&1)==1) {
				if(compare(bd,compare(x,dat[l]))!=bd) { goto lb; }
				x=compare(x,dat[l]);
				l++;
			}
			if((r&1)==0) { sk.Push(r); r--; }
			l>>=1; r>>=1;
		}
		while(sk.Count>0) {
			l=sk.Pop();
			if(compare(bd,compare(x,dat[l]))!=bd) { goto lb; }
			x=compare(x,dat[l]);
		}
		return (-1, x.d);
	lb:
		while(l<<1<cnt) {
			l<<=1;
			if(compare(bd,compare(x,dat[l]))==bd) { x=compare(x,dat[l]); l++; }
		}
		return (l-n, compare(x,dat[l]).d);
	}
}
public class Pt{
	private StringBuilder sb=new StringBuilder();
	public Pt(Action<Pt> f){f(this);}
	public void W(int s){sb.Append(s);}
	public void W(long s){sb.Append(s);}
	public void W(double s){sb.Append(s);}
	public void W(decimal s){sb.Append(s);}
	public void W(char s){sb.Append(s);}
	public void W(string s){sb.Append(s);}
	public void W(object s){sb.Append(s);}
	public void W(params object[] s){sb.Append(string.Join(" ",s));}
	public void Wl(int s){sb.Append(s).AppendLine();}
	public void Wl(long s){sb.Append(s).AppendLine();}
	public void Wl(double s){sb.Append(s).AppendLine();}
	public void Wl(decimal s){sb.Append(s).AppendLine();}
	public void Wl(char s){sb.Append(s).AppendLine();}
	public void Wl(string s){sb.AppendLine(s);}
	public void Wl(object s){sb.Append(s).AppendLine();}
	public void Wl(int[] s){sb.AppendLine(string.Join(" ",s));}
	public void Wl(long[] s){sb.AppendLine(string.Join(" ",s));}
	public void Wl(double[] s){sb.AppendLine(string.Join(" ",s));}
	public void Wl(string[] s){sb.AppendLine(string.Join(" ",s));}
	public void Wl(params object[] s){sb.AppendLine(string.Join(" ",s));}
	public void Wl(){sb.AppendLine();}
	public void Sm(){Console.Write(sb);}
	public void Op(StreamWriter sw){
		sw.Write(sb);
		sw.Close();
	}
	public static bool operator ==(Pt a,Pt b){return a.sb.ToString()==b.sb.ToString();}
	public static bool operator !=(Pt a,Pt b){return a.sb.ToString()!=b.sb.ToString();}
	public override bool Equals(object obj){return false;}
	public override int GetHashCode(){return 0;}
}
public class Sc{
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected virtual string Rl(){return Console.ReadLine();}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected virtual string[] Sp(string st){return st.Split();}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	private T Ct<T>(string s){return (T)Convert.ChangeType(s,typeof(T));}
	public virtual int I{get{return int.Parse(Rl());}}
	public virtual long L{get{return long.Parse(Rl());}}
	public virtual double D{get{return double.Parse(Rl());}}
	public virtual string S{get{return Rl();}}
	public int[] Ia{get{return Array.ConvertAll(Sp(Rl()),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Sp(Rl()),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Sp(Rl()),double.Parse);}}
	public string[] Sa{get{return Sp(Rl());}}
	public object[] Oa{get{return Sp(Rl());}}
	public int[] Ia2{get{return Array.ConvertAll(Sp("0 "+Rl()+" 0"),int.Parse);}}
	public int[] Ia3(string a,string b){return Array.ConvertAll(Sp(a+Rl()+b),int.Parse);}
	public int[] Ia3(int a){return Array.ConvertAll(Sp(Rl()+" "+a.ToString()),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(Sp("0 "+Rl()+" 0"),long.Parse);}}
	public long[] La3(string a,string b){return Array.ConvertAll(Sp(a+Rl()+b),long.Parse);}
	public long[] La3(int a){return Array.ConvertAll(Sp(Rl()+" "+a.ToString()),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(Sp("0 "+Rl()+" 0"),double.Parse);}}
	public double[] Da3(string a,string b){return Array.ConvertAll(Sp(a+Rl()+b),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Sp(Rl()));}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Sp(Rl()));}return a;}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T) Tp2<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T) Tp3<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T,T) Tp4<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T,T,T) Tp5<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]),Ct<T>(s[4]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T,T,T,T) Tp6<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]),Ct<T>(s[4]),Ct<T>(s[5]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T1,T2) Tp2<T1,T2>(){var s=Sp(Rl());return (Ct<T1>(s[0]),Ct<T2>(s[1]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T1,T1,T2) Tp3<T1,T2>(){var s=Sp(Rl());return (Ct<T1>(s[0]),Ct<T1>(s[1]),Ct<T2>(s[2]));}
}
public class Scr:Sc{
	private List<string> li=new List<string>();
	private int l=0;
	private bool bo=false;
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected override string Rl(){
		if(bo){return li[l++%li.Count];}
		li.Add(Console.ReadLine());
		return li[li.Count-1];
	}
	public void Again(){bo=true;}
}
public class Scs:Sc{
	private StreamReader sr;
	private string path;
	public Scs(string path){sr=new StreamReader(this.path=path);}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected override string Rl(){return sr.ReadLine();}
	public void Close(){sr.Close();}
	public void Reset(){sr=new StreamReader(path);}
}
public class Sc2:Sc{
	private string[] sps=new string[]{" ","　","\t"};
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected override string[] Sp(string st){return st.Split(sps,StringSplitOptions.RemoveEmptyEntries);}
	public override int I{get{return int.Parse(Sp(Rl())[0]);}}
	public override long L{get{return long.Parse(Sp(Rl())[0]);}}
	public override double D{get{return double.Parse(Sp(Rl())[0]);}}
	public override string S{get{return Sp(Rl())[0];}}
}
public class Scs2:Sc2{
	private StreamReader sr;
	public Scs2(string t){sr=new StreamReader(t);}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected override string Rl(){return sr.ReadLine();}
	public void Close(){sr.Close();}
}
public class Sct:Sc{
	private List<string> li=new List<string>();
	private int l=0;
	public void Add(int s){li.Add(s.ToString());}
	public void Add(long s){li.Add(s.ToString());}
	public void Add(double s){li.Add(s.ToString());}
	public void Add(string s){li.Add(s.ToString());}
	public void Add(object s){li.Add(s.ToString());}
	public void Add(int[] s){li.Add(string.Join(" ",s));}
	public void Add(long[] s){li.Add(string.Join(" ",s));}
	public void Add(double[] s){li.Add(string.Join(" ",s));}
	public void Add(string[] s){li.Add(string.Join(" ",s));}
	public void Add(params object[] s){li.Add(string.Join(" ",s));}
	protected override string Rl(){return li[l++];}
	public void Clear(){li.Clear();l=0;}
	public void Again(){l=0;}
	public void Pf(){Console.WriteLine(string.Join("\n",li));}
}