#include<bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int N = 1e5 + 10;
const int INF = 1e9;

void solve() {
    int n;
    cin >> n;
    long double ans = 0;
    vector<pair<long double, int>> pp(n + 1);
    vector<pair<long double, ll>> p;
    vector<ll> prec(n + 1);
    for(int i = 1;i <= n ;i ++){
        long double x;
        cin >> x;
        pp[i].first = x;
        cin >> pp[i].second;
    }
    p.push_back({0,0});
    sort(pp.begin() + 1,pp.end());
    long double tmp1 = 0;
    ll tmp2 = pp[1].second;
    for(int i = 2;i <= n;i ++){
        if(pp[i].first == pp[i - 1].first){
            tmp2 += pp[i].second;
        }else {
            p.push_back({pp[i - 1].first,tmp2});
            tmp2 = pp[i].second;
        }
    }
    if(tmp2){
        p.push_back({pp[n].first,tmp2});
    }
    for(int i = 1;i <= p.size() - 1;i ++){
        prec[i] = prec[i - 1] + p[i].second;
    }
    int len = p.size() - 1;
    int r = len + 1;
    for(int i = 1;i <= len;i ++){
        long double maxval = prec[i] / (1 - p[i].first);
        while(r - 1 >= 1){
            long double val = (prec[len] - prec[r - 2]) / p[r - 1].first;
            if(val <= maxval) r --;
            else break;
        }
        ans = max(ans,prec[i] + prec[len] - prec[r - 1] - maxval);
    }
    int l = 0;
    for(int i = n;i >= 1;i --){
        long double maxval = (prec[len] - prec[i - 1]) / p[i].first;
        while(l + 1 <= n){
            long double val = prec[l + 1] / (1 - p[l + 1].first);
            if(val < maxval) l ++;
            else break;
        }
        ans = max(ans,prec[len] - prec[i - 1] + prec[l] - maxval);
    }
    cout << fixed << setprecision(10) << ans << "\n";
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    
    int t = 1;
    // cin >> t;
    while(t -- ) {
        solve();
    }

    return 0;
}