/*
* Author: Nonoze
* Created: Tuesday 23/12/2025
*/
#include <bits/stdc++.h>
using namespace std;
#ifndef DEBUG
#define dbg(...)
#endif
// #define cout cerr << "OUT: "
#define endl '\n'
#define endlfl '\n' << flush
#define quit(x) return (void)(cout << x << endl)
template<typename T> void read(T& x) { cin >> x; }
template<typename T1, typename T2> void read(pair<T1, T2>& p) { read(p.first), read(p.second); }
template<typename T> void read(vector<T>& v) { for (auto& x : v) read(x); }
template<typename T1, typename T2> void read(T1& x, T2& y) { read(x), read(y); }
template<typename T1, typename T2, typename T3> void read(T1& x, T2& y, T3& z) { read(x), read(y), read(z); }
template<typename T1, typename T2, typename T3, typename T4> void read(T1& x, T2& y, T3& z, T4& zz) { read(x), read(y), read(z), read(zz); }
template<typename T> void print(vector<T>& v) { for (auto& x : v) cout << x << ' '; cout << endl; }
#define sz(x) (int)(x.size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define make_unique(v) sort(all(v)), v.erase(unique(all(v)), (v).end())
#define pb push_back
#define mp(a, b) make_pair(a, b)
#define fi first
#define se second
#define cmin(a, b) a = min(a, b)
#define cmax(a, b) a = max(a, b)
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define QYES quit("YES")
#define QNO quit("NO")
#define int long long
#define double long double
const int inf = numeric_limits<int>::max() / 4;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9+7, LOG=20;
void solve();
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
int tt=1;
// cin >> tt;
while(tt--) solve();
return 0;
}
int n, k, m, q;
vector<double> a, b;
void solve() {
read(n);
a.assign(n, 0), b.assign(n, 0);
for (int i=0; i<n; i++) read(a[i], b[i]);
sort(all(a)), sort(all(b));
double res=0, acta=0, actb=0;
int cnt=0;
for (int i=0; i<n; i++) {
acta+=a[n-i-1];
cnt=i+1, actb=0;
for (int j=0; j<n; j++) {
actb+=b[n-j-1];
cnt++;
cmax(res, min(acta, actb) - cnt);
}
}
// while (!a.empty() || !b.empty()) {
// if (a.empty()) {
// actb+=b.back();
// b.pop_back();
// cnt++;
// } else if (b.empty()) {
// acta+=a.back();
// a.pop_back();
// cnt++;
// } else if (acta < actb) {
// acta+=a.back();
// a.pop_back();
// cnt++;
// } else {
// actb+=b.back();
// b.pop_back();
// cnt++;
// }
// cmax(res, min(acta, actb) - cnt);
// }
cout << fixed << setprecision(4) << res << endl;
}
