#include<iostream>
#include <bits/stdc++.h>

#define ld long double
#define ll long long
#define IO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
const int N = 3e5 + 9, MOD = 998244353;


void doWork() {
    int n, t;
    cin >> n >> t;
    vector<pair<int, int> > v(n);
    for (int i = 0; i < n; i++) {
        cin >> v[i].first >> v[i].second;
    }

    ld low = -1e9, high = 1e10;
    while (high - low > 1e-7) {
        ld m = (low + high) / 2;
        ld sum = 0;
        for (auto i: v) {
            if (i.second + m <= 0) {
                sum = 1e18;
                break;
            }
            sum += i.first / (i.second + m);
        }
        if (sum > t) low = m;
        else high = m;
    }
    cout << fixed << setprecision(9) << low;
}

int main() {
    IO
    int t = 1;
//    cin >> t;
    for (int i = 1; i <= t; i++) {
        //  cout << "Case #" << i << ": ";
        doWork();
    }
}