#include<bits/stdc++.h>
#pragma GCC target("avx2")
#define rep(i, a, b) for (ll i = (a); i < (b); i++)
#define all(x) (x).begin(), (x).end()
#define sz(x) (ll)size(x)
using namespace std;
using ll = long long;
using vi = vector<ll>;
using vvi = vector<vi>;
using pii = pair<ll, ll>;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

void solve() {
    auto start = chrono::steady_clock::now();
    ll n, w;
    cin >> n >> w;
    vector<pii> mills(n);
    for (auto& [x, y] : mills) {
        cin >> x >> y;
    }
    cout << setprecision(9) << fixed;
    double lo = 0, hi = 1e10;
    while (chrono::steady_clock::now() - start < chrono::milliseconds(250)) {
        double mid = (lo + hi) / 2;
        double kgsprocessed = 0;
        for (auto [p, t] : mills) {
            kgsprocessed += max(0., mid - 2 * t) * p;
        }
        (kgsprocessed >= w ? hi : lo) = mid;
    }
    cout << lo << endl;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    solve();

    return 0;
}