#include <bits/stdc++.h>
#define ll long long
#define all(aaa) aaa.begin(), aaa.end()
using namespace std;
#define int long long
int getInt(string s) {
int x = 0;
for (char c : s) {
if (c != '.')
x = x * 10 + c - '0';
}
int y = 0;
while (*(s.end() - y - 1) != '.')
y++;
while (y++ < 4)
x *= 10;
return x;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
int n;
cin >> n;
multiset<int> sta, stb;
for (int i = 0; i < n; i++) {
string a, b;
cin >> a >> b;
// cout << getInt(a) << " " << getInt(b) << "\n";
sta.insert(getInt(a));
stb.insert(getInt(b));
}
int sa = 0, sb = 0, ans = 0;
for (int i = 1; i <= 2 * n; i++) {
if (sa > sb) {
if (stb.empty())
break;
sb += *stb.rbegin();
stb.erase(prev(stb.end()));
}
else {
if (sta.empty())
break;
sa += *sta.rbegin();
sta.erase(prev(sta.end()));
}
ans = max(ans, min(sa, sb) - i * 10000);
}
string s;
while (ans > 0) {
s.push_back(ans % 10 + '0');
ans /= 10;
}
while (s.size() < 5)
s.push_back('0');
reverse(all(s));
s.insert(s.end() - 4, '.');
cout << s;
return 0;
}
