#include <bits/stdc++.h>
#define int long long
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
using namespace std;
const int MULT=1000000;
signed main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int n; cin >> n;
vector<int> a(n);
vector<int> b(n);
for (int i = 0; i < n; i++)
{
double _a,_b; cin >> _a >> _b;
_a*=MULT;
_b*=MULT;
a[i]=(int)_a-MULT;
b[i]=(int)_b-MULT;
}
sort(rall(a));
sort(rall(b));
int i=0;
int j=0;
int lsum=0;
int rsum=0;
int mn=0;
while(i<n||j<n){
int _i=i;
int _j=j;
if((lsum<rsum||(lsum==rsum&&a[i]<b[j]))&&i<n){
lsum+=a[i];
rsum-=MULT;
i++;
}else if(j<n){
rsum+=b[j];
lsum-=MULT;
j++;
}
if(_i==i&&_j==j) break;
mn=max(min(lsum,rsum),mn);
}
double ans=(double)mn/(double)MULT;
cout << setprecision(5) << ans << "\n";
return 0;
}
