#include<bits/stdc++.h>
using namespace std;
int n;
double sum[1000005];
constexpr double eps=1e-8;
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]-calc(1),mx=-1e18;
    int pos=0;
    for(int i=2;i<=n;i++)if(v[i-1].first-eps>v[i-2].first){
        pos++;
        double k=calc(i);
        while(calcw(pos)-eps>=k) pos--;
        ans=max(ans,sum[n]-sum[i-1]+max(sum[pos]-k,mx));
        // cout<<ans<<' '<<pos<<' '<<mx<<' '<<k<<'\n';
        mx=max(sum[i]-calcw(i),mx);
    }
    cout<<fixed<<setprecision(10)<<max(ans,0.0)<<'\n';
}