#include <bits/stdc++.h>
using namespace std;
const double EXP=1e-6;
int T,m=0,n=0;
double a[100005],b[100005];
bool Check(double lim)
{
for(int i=1;i<=m;i++)
{
int lim2=min(int(max(a[i]-lim,0.0)),n);
if(b[lim2]-double(i)>=lim)
return true;
}
return false;
}
int main()
{
ios_base::sync_with_stdio(false);
//freopen("TEST.INP","r",stdin);
cin>>T;
double x,y;
while(T--)
{
cin>>x>>y;
if(x>=1.0)
a[++m]=x-1.0;
if(y>=1)
b[++n]=y-1.0;
}
sort(a+1,a+m+1,greater<double>());
sort(b+1,b+n+1,greater<double>());
for(int i=1;i<=m;i++)
a[i]+=a[i-1];
for(int i=1;i<=n;i++)
b[i]+=b[i-1];
double res,l=0,r=1e9;
while(r-l>=EXP)
{
double mid=(l+r)/2.0;
if(Check(mid)==true)
{
res=mid;
l=mid+EXP;
}
else
r=mid-EXP;
}
cout<<setprecision(4)<<fixed<<res;
}
