#include <bits/stdc++.h>

#define prm(x) x.begin(), x.end()
#define srt(x) sort(prm(x))
#define rvs(x) reverse(prm(x))

using namespace std;
using ll = long long;
using ld = long double;

int main()
{
    cout << setprecision(6);
    cout << fixed;
    const long double EPS = 1e-7;
    ld l = -1e9, r = 1e9, m;
    ll t, g;
    cin >> t >> g;
    vector<pair<ll, ll>> v(t);
    for (auto &cl : v)
    {
        cin >> cl.first >> cl.second;
    }
    while (abs(l - r) > EPS)
    {
        m = l + (r - l) / 2;
        ld sum = 0;
        for (auto &cl : v)
        {
            if (cl.second + m <=0){
                sum=1e9;
                break;
            }
            sum += cl.first / (cl.second + m);
        }
        if (g < sum)
        {
            l = m;
        }
        else
        {
            r = m;
        }
    }
    cout << m << endl;
    return 0;
}