#include <bits/stdc++.h>  
using namespace std;  

#define int long long  

using db = double;

constexpr db eps = 1e-9;

int sgn(db x) {
	if (x > eps) {
		return 1;
	} else if (x < -eps) {
		return -1;
	}
	return 0;	
}

int cmp(db x, db y) {
	return sgn(x - y);
}

signed main() {  
    ios::sync_with_stdio(false);
    cin.tie(nullptr);  

	int n;
	cin >> n;
 
 	vector<double> p(n + 1);
 	vector<int> c(n + 1);

 	for (int i = 1; i <= n; i++) {
 		cin >> p[i] >> c[i];
 	}

 	vector<int> ord(n + 1);
 	iota(ord.begin(), ord.end(), 0);

 	sort(ord.begin() + 1, ord.end(), [&](int i, int j) {
 		return p[i] > p[j];
 	});

 	vector<double> a(1, -1);
 	vector<int> b(1);
 	for (int i = 1; i <= n; i++) {
 		if (cmp(p[ord[i]], a.back()) == 0) {
 			b[b.size() - 1] += c[ord[i]];
 		} else {
 			a.push_back(p[ord[i]]);
 			b.push_back(c[ord[i]]);
 		}
 	}

 	n = a.size() - 1;

 	// for (int i = 1; i <= n; i++) {
 	// 	cout << a[i] << " \n"[i == n];
 	// }
 	// for (int i = 1; i <= n; i++) {
 	// 	cout << b[i] << " \n"[i == n];
 	// }
 	
 	vector<int> pre(n + 1), suf(n + 2);
 	for (int i = 1; i <= n; i++) {
 		pre[i] = pre[i - 1] + b[i];
 	}
 	for (int i = n; i >= 1; i--) {
 		suf[i] = suf[i + 1] + b[i];
 	}

 	double ans = 0;

 	for (int i = 0; i <= n; i++) {
 		if (cmp(a[i], 0) == 0) {
 			break;
 		}
 		double x = i == 0 ? 0 : 1.0 / a[i];
 		double sx = pre[i];

	 	auto calc = [&](int b) {
	 		int pos = n + 1 - b;
	 		if (cmp(a[pos], 1) == 0) {
	 			return -1e18;
	 		}
	 		// cout << pos << "\n";
	 		double y = b == 0 ? 0 : 1.0 / (1 - a[pos]);
			double sy = suf[pos];
			// cout << x << " " << y << " " << sx << " " << sy << " " << sx + sy - max(sx * x, sy * y) << "\n";
			return sx + sy - max(sx * x, sy * y);
	 	};
 		int l = 0, r = n - i;
 		while (r - l > 5) {
 			int lm = (2 * l + r) / 3, rm = (l + 2 * r) / 3;
 			if (calc(lm) < calc(rm)) {
 				l = lm;
 			} else {
 				r = rm;
 			}
 		}
 		for (int j = l; j <= r; j++) {
 			ans = max(ans, calc(j));
 		}
 	}

 	cout << fixed << setprecision(10);
 	cout << ans << "\n";

    return 0;
}