#include <bits/stdc++.h>
using namespace std;
using ld = long double;
const ld eps = 1e-6;
struct pkt {
ld x, y;
pkt(ld a=0, ld b=0): x(a), y(b) {}
friend pkt operator+(const pkt &a, const pkt &b){ return {a.x+b.x, a.y+b.y}; }
friend pkt operator-(const pkt &a, const pkt &b){ return {a.x-b.x, a.y-b.y}; }
friend pkt operator*(const pkt &a, ld b){ return {a.x*b, a.y*b}; }
friend pkt operator/(const pkt &a, ld b){ return {a.x/b, a.y/b}; }
friend ld operator*(const pkt &a, const pkt &b){ return a.x*b.y - a.y*b.x; } // cross product
bool z() const { return y < 0 || (y == 0 && x < 0); }
bool operator<(const pkt &b) const {
if(z() != b.z()) return z() < b.z();
return (*this)*b < 0;
}
bool operator==(const pkt &b) const { return abs(x-b.x)<eps && abs(y-b.y)<eps; }
};
inline ld d(const pkt &a, const pkt &b){ return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)); }
int n, k, s, t;
pkt ar[703];
bool eqd(ld a, ld b){ return abs(a-b)<eps || abs((a-b)/min(a,b)) < eps; }
// Check if radius r can cover k stars
bool da(ld r){
for(int i=0;i<n;i++){
if(d(ar[i], {0,0})*s > r) continue;
if(k==1) return true;
vector<pair<pkt,pkt>> intervals;
for(int j=0;j<n;j++){
if(i==j) continue;
pkt o = (ar[i]+ar[j])/2;
pkt a = ar[j]-ar[i];
if(s*d({0,0}, ar[j])+t*d(ar[i],ar[j]) > r) continue;
// rotate 90 degrees
swap(a.x, a.y); a.y = -a.y;
ld p=-1e9, q=1e9;
while(!eqd(p,q)){
ld l=(51*p+50*q)/101;
ld m=(p+q)/2;
ld r1 = s*d({0,0}, o+a*l) + t*d(ar[i], o+a*l);
ld r2 = s*d({0,0}, o+a*m) + t*d(ar[i], o+a*m);
if(r1 < r2) q=m; else p=l;
}
pkt first = o + a*p;
pkt second = o - a*p;
first = first - ar[i];
second = second - ar[i];
if((first*second)>0) swap(first, second);
intervals.push_back({first, second});
}
if(intervals.empty()) continue;
vector<pair<pkt,bool>> events;
for(auto &[l,r]: intervals){
events.push_back({l,0});
events.push_back({r,1});
}
sort(events.begin(), events.end());
int S=0, M=0;
for(auto &[p,flag]: events){
if(flag) S--; else S++;
M = max(M,S);
}
if(M+1 >= k) return true;
}
return false;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> k >> n >> s >> t;
for(int i=0;i<n;i++) cin >> ar[i].x >> ar[i].y;
sort(ar, ar+n, [](pkt a, pkt b){ return d(a,{0,0}) < d(b,{0,0}); });
ld lo=0, hi=1e18;
for(int it=0;it<100;it++){
ld mid = (lo+hi)/2;
if(da(mid)) hi = mid;
else lo = mid;
}
cout << fixed << setprecision(12) << hi << "\n";
return 0;
}
