#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
#define all(x) x.begin(), x.end()
template <typename T1, typename T2> inline void chkmin(T1 &x, const T2 & y) {if (x > y) x = y;}
template <typename T1, typename T2> inline void chkmax(T1 &x, const T2 & y) {if (x < y) x = y;}
int Read() {
string s;
cin >> s;
int ans = 0;
int cnt = 4;
bool flag = false;
for (auto i : s) {
if (i == '.') {
flag = true;
continue;
}
if (flag) cnt--;
ans *= 10;
ans += i - '0';
}
while (cnt--)
ans *= 10;
return ans;
}
int n;
vector<ll> a, b;
void read() {
cin >> n;
a.resize(n);
b.resize(n);
for (int i = 0; i < n; i++) {
a[i] = Read();
b[i] = Read();
}
}
ll solve(vector<ll> a, vector<ll> b) {
ll ans = 0;
for (int i = 1; i < n; i++) {
a[i] += a[i - 1];
b[i] += b[i - 1];
}
for (int i = 0; i < n; i++) {
ll pos = lower_bound(all(b), a[i]) - b.begin();
if (pos == n) break;
chkmax(ans, a[i] - (i + 1) * 10000 - (pos + 1) * 10000);
}
return ans;
}
ll ans;
void run() {
sort(all(a));
reverse(all(a));
sort(all(b));
reverse(all(b));
ans = max(solve(a, b), solve(b, a));
}
string get(ll ans) {
string fans = "";
for (int i = 0; i < 4; i++) {
fans += '0' + ans % 10;
ans /= 10;
}
fans += ".";
if (ans == 0) {
fans += "0";
}
else {
while (ans) {
fans += '0' + ans % 10;
ans /= 10;
}
}
reverse(all(fans));
return fans;
}
void write() {
cout << get(ans) << endl;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
read();
run();
write();
return 0;
}
