95分，必关

#include<bits/stdc++.h>
using namespace std;
int a[100010],b[100010];
int n,p;
double num;
bool check(double x){
	double ans=0;
	for(int i=1;i<=n;i++){
		if(b[i]<a[i]*x){
			ans+=a[i]*x-b[i];
		}
	}
	if(ans<=p*x){
		return 1;
	}else{
		return 0;
	}
}
int main(){
	cin>>n>>p;
	for(int i=1;i<=n;i++){
		cin>>a[i]>>b[i];
		num+=a[i];
	}
	if(num<=p){
		cout<<-1;
		return 0;
	}
	double l=0,r=1e9;
	while(l+0.0000001<r){
		double mid=(l+r)/2;
		if(check(mid)){
			l=mid;
		}else{
			r=mid;
		}
	}
	cout<<l;
	return 0;
}