#include<bits/stdc++.h>
using namespace std;
int n;
#define double long double
double sum[1000005];
constexpr double eps=1e-9;
int main(){
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    cin>>n;vector<pair<double,int>>v(n);
    for(auto&x:v) cin>>x.first>>x.second;
    sort(v.begin(),v.end());
    for(int i=1;i<=n;i++) sum[i]=sum[i-1]+v[i-1].second;
    auto calc=[&](int x) -> double {
        if(v[x-1].first>eps) return 1/v[x-1].first*(sum[n]-sum[x-1]);
        else return 1e18;
    };
    auto calcw=[&](int x) -> double {
        if(1-v[x-1].first>eps) return 1/(1-v[x-1].first)*sum[x];
        else return 1e18;
    };
    double ans=sum[n]-min(calc(1),calcw(n));
    int pos=n;
    for(int i=2;i<=n;i++)
    if(v[i-1].first-eps>v[i-2].first){
        double k=calc(i);
        while(pos>0&&(calcw(pos)-eps>=k||v[pos].first-eps<=v[pos-1].first)) pos--;
        if(pos<1) break;
        if(pos>=i) ans=max(ans,sum[n]-k);
        ans=max(ans,sum[n]-sum[i-1]+sum[pos]-k);
    }pos=1;
    for(int i=n-1;i>=1;i--)
    if(v[i].first-eps>v[i-1].first){
        double k=calcw(i);
        while(pos<=n&&(calc(pos)-eps>=k||v[pos-1].first-eps<=v[pos-2].first)) pos++;
        if(pos>n) break;
        if(pos<=i) ans=max(ans,sum[n]-k);
        ans=max(ans,sum[i]+sum[n]-sum[pos-1]-k);
        // cout<<ans<<' '<<pos<<' '<<k<<'\n';
    }
    cout<<fixed<<setprecision(10)<<max<double>(ans,0.0)<<'\n';
}