#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define all(A) A.begin(),A.end()
#define bp '\n'
#define vp cout<<'\n';
const int N=2e5+5;
signed main(){
cin.tie(nullptr)->sync_with_stdio(false);
int n;
cin>>n;
vector<pair<double,double>>a(n);
double ans=-1e18;
for(int i=0;i<n;++i){
cin>>a[i].first>>a[i].second;
}
for(int i=0;i<(1<<n);++i){
for(int j=0;j<(1<<n);++j){
double s1=0,s2=0,sel=0;
for(int k=0;k<n;++k){
if(i&(1<<k)){
s1+=a[k].first;
++sel;
}
if(j&(1<<k)){
s2+=a[k].second;
++sel;
}
}
//cout<<s1<<' '<<s2<<bp;
ans=max(ans,min(s1,s2)-sel);
}
}
cout<<fixed<<setprecision(4)<<ans;
}
/*
5 9 7
...##....
..#.##..#
..#....##
.##...#..
....#....
WSEE
*/
