#include<bits/stdc++.h>
#define LL long long
#define len(G) (LL)(G).size()
#define all(G) (G).begin(),(G).end()
#define ar(n) array<LL,n>
using namespace std;
using i128=__int128;
using ar=array<LL,2>;
using Poly=vector<LL>;

mt19937_64 rnd(random_device{}());

constexpr LL N=2e5+9;
constexpr double eps=1e-10;
using numbers::pi;

LL n,K;
double t[N];

template<class T>
inline void read(T &x)
{
	x=0;int w=1;char c=getchar();
	while(!isdigit(c)){if(c=='-')w=-1;	c=getchar();}
	while(isdigit(c)){x=x*10+(c^'0');	c=getchar();}
	if(w==-1)	x=-x;
}
template<class T,class... Args>
inline void read(T &x,Args &...args)
{
	read(x),read(args...);
}

double ang(double x,double y)
{
	double t=atan2(y,x);
	if(t<0)	t+=2*pi;
	return t;
}

// map<double,LL> mp;
vector<pair<double,LL>> G;
void add(double l,double r)
{
	// ++mp[l-eps];
	// --mp[r+eps];
	G.push_back({l-eps,1});
	G.push_back({r+eps,-1});
}

bool check(double a)
{
	// mp.clear();
	// mp[2*pi+eps]=0;
	G.clear();
	G.push_back({2*pi+eps,0});
	for(LL i=1;i<=n;++i)
	{
		double l=t[i]-a/2,r=t[i]+a/2;
		if(l<0)
		{
			add(0,r);
			add(l+2*pi,2*pi);
		}
		else if(r>2*pi)
		{
			add(0,r-2*pi);
			add(l,2*pi);
		}
		else
		{
			add(l,r);
		}
	}
	sort(all(G));
	// if(mp.begin()->first>0)	return 0;
	// if(G.begin()->first>0)	return 0;
	LL cur=0;
	for(auto [k,v]:G)
	{
		if(k>0&&cur<K)	return 0;
		if(k>2*pi)	break;
		cur+=v;
	}
	return 1;
}

void solve()
{
	read(n,K);
	for(LL i=1;i<=n;++i)
	{
		LL x,y;
		read(x,y);
		t[i]=ang(x,y);
	}
	double l=0,r=2*pi;
	for(LL _=1;_<=30;++_)
	{
		double mid=(l+r)/2;
		if(check(mid))	r=mid;
		else	l=mid;
	}
	printf("%.10lf\n",l);
}

int main()
{
	LL T;
	read(T);
	while(T--)	solve();
	return 0;
}