// Coded by hjxddl
#include <bits/stdc++.h>
#define ll long long
#define db long double
const int N = 2e5 + 5;
const db eps = 1e-6;
int n;
std::vector<ll> pre;
std::vector<std::pair<db, ll>> a, b;
db cul(int l, int r) {
    ll sx = pre[l], sy = pre[n] - pre[r - 1];
    if (a[l].first == 0 || a[r].first == 1)
        return 0;
    return sx + sy - std::max(sx / b[l].first, sy / (1 - b[r].first));
}
void solve() {
    std::cin >> n;
    a.resize(n + 5), pre.resize(n + 5);
    for (int i = 1; i <= n; i++) {
        std::cin >> a[i].first >> a[i].second;
        a[i].first *= -1;
    }
    std::sort(a.begin() + 1, a.begin() + n + 1);
    b.push_back({0, 0});
    for (int i = 1; i <= n; i++) {
        ll sum = a[i].second;
        while (i < n && a[i].first == a[i + 1].first)
            i++, sum += a[i].second;
        b.push_back({-a[i].first, sum});
    }
    n = b.size() - 1;
    for (int i = 1; i <= n; i++)
        pre[i] = pre[i - 1] + b[i].second;
    db ans = 0;
    for (int i = 1; i < n; i++) {
        int l = i + 1, r = n, lmid = l + (r - l + 1) / 3, rmid = r - (r - l + 1) / 3;
        while (l < r) {
            db s1 = cul(i, lmid), s2 = cul(i, rmid);
            if (fabs(s1 - s2) <= eps) {
                l = lmid + 1;
                r = rmid - 1;
            } else if (s1 > s2) {
                r = rmid - 1;
            } else if (s1 < s2) {
                l = lmid + 1;
            }
            lmid = l + (r - l + 1) / 3, rmid = r - (r - l + 1) / 3;
        }
        ans = std::max(ans, cul(i, l));
    }
    std::cout << std::fixed << std::setprecision(12) << ans << '\n';
}
int main() {
    std::ios::sync_with_stdio(0);
    std::cin.tie(0), std::cout.tie(0);
    int t = 1;
    while (t--) {
        solve();
    }
}