#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
int get(int x1,int y1,int x2,int y2)
{
	int d=(x2-x1)*2-(y1%2);
	int pymin=y1+(y1%2),pymax=y1+(x2-x1)*2-(y1%2);
	if (pymin>y2)
		d+=(pymin-y2);
	else if (pymax<y2)
		d+=(y2-pymax);
	return d;
}
int main()
{
	freopen("ha14c.in","r",stdin);
	freopen("ha14c.out","w",stdout);
	int n,m,k,s;
	scanf("%d%d%d%d",&n,&m,&k,&s);
	int ans=(1<<30);
	int xa,ya;
	scanf("%d%d",&xa,&ya);
	for (int i=0;i<m;i++)
	{
		int xi,yi;
		scanf("%d%d",&xi,&yi);
		if (xi<xa)
			ans=min(ans,get(xi,yi,xa,ya));
		if (xi==xa)
			ans=min(ans,abs(ya-yi));
		if (xi>xa)
			ans=min(ans,get(xa,ya,xi,yi));
	}
	if (k*ans+1<=s)
		cout<<s-(k*ans+1)<<endl;
	else
		cout<<-1<<endl;
	return 0;
}