#include <bits/stdc++.h>
#define f(i, s, k, l) for (int i = s; i < k; i += l)
#define for0(i, k) f(i, 0, k, 1)

#define pl pair<long long, long long>
#define pb push_back

#define vl vector<long long>
#define vi vector<int>
#define sz(x) (ll)(x).size()

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

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

    ll n;
    ld w;
    cin >> n >> w;
    vector<ld> wph(n), time(n);
    for0(i, n) cin >> wph[i] >> time[i];

    ld l = 0;
    ld r = 1e18;

    for0(i, 200) {
        ld mid = (l + r) / 2.0;
        ld sum = 0;
        for0 (i, n) {
            if (2 * time[i] >= mid) continue;
            sum += (mid - 2 * time[i]) * wph[i];
        }
        if (sum < w) l = mid;
        else r = mid;
    }
    cout << fixed << setprecision(10) << r << endl;
}