#include<bits/stdc++.h>
#ifndef xxx
#define dbg(...) ;
#endif
using namespace std;
template<class T> ostream &operator<<(ostream &o, const vector <T> &v) { bool f=false; for(T i:v) { f?o<<' ':o; o<<(i); f=true; } return o; }
template<class T> void sort(T &v) { std::sort(v.begin(), v.end()); }
template<class T, class C> void sort(T &v, C c) { std::sort(v.begin(), v.end(), c); }
template<class T> void reverse(T &v) { std::reverse(v.begin(), v.end()); }
template<class T> bool is_sorted(T &v) { return std::is_sorted(v.begin(), v.end()); }
template<class T> inline void _min(T &x, const T &y) { x>y?x=y:x; }
template<class T> inline void _max(T &x, const T &y) { x<y?x=y:x; }
istream &operator>>(istream &i, __int128_t &x) { x=0; short f=1; char c=0; while(!isdigit(c)) { if(c=='-')f=-1; c=i.get(); } while(isdigit(c))x=x*10+c-'0', c=i.get(); x*=f; return i; }
ostream &operator<<(ostream &o, __int128_t x) { if(x==0) { o<<0; return o; } bool f=false; string s; if(x<0)f=true, x=-x; while(x)s+=x%10+'0', x/=10; reverse(s); if(f)o<<'-'; o<<s; return o; }
mt19937 mt(time(0));
typedef long double db;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
constexpr int maxn=2e5+5;
constexpr int mod=1e9+7;
constexpr int inf=0x3f3f3f3f;
constexpr ll INF=0x3f3f3f3f3f3f3f3fll;
constexpr double pi=acos(-1.0);
constexpr double eps=1e-9;
pii p[maxn];
int main()//MARK: main
{
#ifndef xxx
	ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#endif
	cout<<fixed<<setprecision(10);
	int n, k;
	cin>>n>>k;
	for(int i=1; i<=n; i++)
		cin>>p[i].first>>p[i].second;
	auto check=[&](db m)->bool
	{
		set<db>se;
		for(int i=n; i>=k-1; i--)
		{
			auto [x, y]=p[i];
			db v=y-m*x;
			if(i<=n-1&&se.lower_bound(v)!=se.end())
			{
				return true;
			}
			se.insert(v);
		}
		return false;
	};
	db l=-inf, r=inf;
	for(int i=1; i<=60; i++)
	{
		db mid=(l+r)/2;
		if(check(mid))
		{
			l=mid;
		}
		else
		{
			r=mid;
		}
		if(l>r)break;
	}
	cout<<l<<'\n';
	return 0;
}