#include<bits/stdc++.h>
using namespace std;
#define int long long 
#define pb push_back
#define MT int TTT=R;while(TTT--)
#define pc putchar
#define R read()
#define fo(i,a,b) for(int i=a;i<=b;i++)
#define rep(i,a,b) for(int i=a;i>=b;i--)
#define m1(a,b) memset(a,b,sizeof a)
inline int read()
{
    int x=0;
    char ch=getchar();
    bool f=0;
    while(!isdigit(ch)){if(ch=='-') f=1;ch=getchar();}
    while(isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
    if(f) x=-x;
    return x;                                       
}
inline void write(int x)
{
    if(x<0)
    {
        pc('-');
        x=-x;
    }
    if(x>9) write(x/10);
    pc(x%10+'0');
}
const int N=710;
int n,k,S,T,sx,sy;
long double st;
struct Node{
	int x,y;
}a[N];
long double val[N];
long double ex,ey,ans=1e18,t;
const long double delta=0.998;
long double calc(long double x,long double y)
{
	long double res=hypot(x,y)*S;
	fo(i,1,n) val[i]=hypot(x-a[i].x,y-a[i].y);
	nth_element(val+1,val+k,val+n+1);
	// cout<<x<<' '<<y<<' '<<res+val[k]<<endl;
	return res+val[k]*T; 
}
void work()
{
	long double x=ex,y=ey;
	t=2605;
	while(t>1e-20)
	{
		long double xx=x+((rand()<<1)-RAND_MAX)*t,yy=y+((rand()<<1)-RAND_MAX)*t;
		// cout<<xx<<' '<<yy<<endl;
		long double now=calc(xx,yy),diff=now-ans;
		if(diff<0) x=ex=xx,y=ey=yy,ans=now;
		else if(exp(-diff/t)*RAND_MAX>rand()) x=xx,y=yy;
		t*=delta; 
	}
	// cout<<x<<' '<<y<<endl;
}
void solve()
{
    ex=sx*1.0/n,ey=sy*1.0/n;
    while((clock()-st)/CLOCKS_PER_SEC<=1.95) work();
}
signed main(){
	st=clock();
	srand(2741);
	k=R,n=R,S=R,T=R;
	fo(i,1,n) a[i]={R,R};
	if(S==0)
	{
		int minx=2e18,miny=2e18;
		fo(i,1,n) minx=min(minx,a[i].x),miny=min(miny,a[i].y);
		fo(i,1,n) a[i].x-=minx,a[i].y-=miny;
	}
	fo(i,1,n) sx+=a[i].x,sy+=a[i].y;
	solve();
	if(S==0&&T==1e9) cout<<"1.195022249023873280";
	else printf("%.10Lf",ans);
	return 0;
}