#include <bits/stdc++.h>
#define int long long
#define double long double

const double eps = 1e-10;

void solve() {
    int n;
    std::cin >> n;
    std::vector < std::pair < double , int > > a(n);
    for(auto &[x, y] : a) std::cin >> x >> y;
    std::vector < std::pair < double , int > > used;
    std::sort(a.begin(), a.end());
    used.emplace_back(0, 0);
    for(int i = 0; i < a.size(); ++i) {
        if(used.size() == 1) {
            used.emplace_back(a[i]);
            continue;
        }
        if(fabs(used.back().first - a[i].first) < eps) {
            used.back().second += a[i].second;
        } else {
            used.emplace_back(a[i]);
        }
    }
    int len = used.size() - 1;
    std::vector < int > sum(len + 1);
    for(int i = 1; i <= len; ++i) {
        sum[i] = sum[i - 1] + used[i].second;
        // std::cout << used[i].first << ' ' << used[i].second << '\n';
    }
    double ans = 0;
    for(int r = len, l = 1; r >= 1; --r) {
        // if(used[r].first == 0) continue;
        double now = (sum[n] - sum[r - 1]) / used[r].first;
        while(l < r && sum[l] / (1 - used[l].first) < now) ++l;
        ans = std::max(ans, 1.0 * (sum[n] - sum[r - 1]) + 1.0 * sum[l - 1] - now);
        if(l >= r) break;
        ans = std::max(ans, 1.0 * (sum[n] - sum[r - 1]) + 1.0 * sum[l] - 1.0 * sum[l] / (1.0 - used[l].first));
    }
    std::cout << std::fixed << std::setprecision(10) << ans << '\n';
}

signed main() {
    std::cin.tie(nullptr) -> sync_with_stdio(false);
    int T = 1;
    while(T--) solve();
    return 0;
}