//In the name of GOD
#include <bits/stdc++.h>
using namespace std;
typedef tuple<long double, bool, int> tpi3;
const int maxN=5e2+5, maxA=1e3+5, inf=1e6;
int n, k, a[maxN], b[maxN], mark[maxN];
bool can(long double t){
fill(mark+1, mark+n+1, 0);
long double m=t;
int v=1, cnt=0;
while(cnt<n){
tpi3 maxi={-inf, false, 0};
for (int i=1; i<=n; i++){
if(mark[i]<1) maxi=max(maxi, {m-a[i], false, i});
if(mark[i]<2 and b[i]>0) maxi=max(maxi, {(t-((long double)(b[i])/v))*(v+1), true, i});
}
if(get<0>(maxi)<0) break;
cnt+=(mark[get<2>(maxi)]<1);
mark[get<2>(maxi)]++;
t-=(long double)(get<1>(maxi) ? b[get<2>(maxi)] : a[get<2>(maxi)])/v;
v+=get<1>(maxi);
m=t*v;
}
return (cnt>=k);
}
int main(){
cin >>n >>k;
for (int i=1; i<=n; i++)
cin >>a[i] >>b[i];
long double l=0, r=maxN*maxA;
while(r-l>0.00001){
long double mid=(r+l)/2;
if(can(mid)) r=mid;
else l=mid;
}
cout <<fixed <<setprecision(10) <<r <<endl;
}
