#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define ew "\n"
#define all(x) (x).begin(), (x).end()
#define st first
#define nd second
#define len(x) (int)x.size()
#define eb emplace_back
#define turbo \
ios_base::sync_with_stdio(false); \
cin.tie(0); \
cout.tie(0);
const int maxn = 5e5 + 12;
const int mxx = 100100;
const int MOD = 1e9 + 7;
const int inf = 2e18 + 7;
const int HH = 1e2 + 70;
int n;
long double a[maxn], b[maxn];
void code()
{
cin >> n;
for (int i = 1; i <= n; i++)
{
cin >> a[i] >> b[i];
}
sort(a + 1, a + n + 1);
sort(b + 1, b + n + 1);
reverse(b + 1, b + n + 1);
reverse(a + 1, a + n + 1);
double rs = 0;
vector<double> aa(n + 1, 0), bb(n + 1, 0);
for (int i = 1; i <= n; i++)
{
aa[i] = aa[i - 1] + a[i];
bb[i] = bb[i - 1] + b[i];
}
for (int md = 0; md <= 2 * n; md++)
{
int L = max(0ll, md - n);
int R = min(md, n);
if (L > R)
{
continue;
}
int l = L, r = R;
int x = L;
double cur = fabsl(aa[L] - bb[md - L]);
while (l <= r)
{
int mid = (l + r) >> 1;
double dif = aa[mid] - bb[md - mid];
if (fabsl(dif) < cur)
{
cur = fabsl(dif);
x = mid;
}
if (dif < 0)
{
l = mid + 1;
}
else
{
r = mid - 1;
}
}
for (int to = max(L, x - 1); to <= min(R, x + 1); to++)
{
double v = min(aa[to], bb[md - to]) - md;
rs = max(rs, v);
}
}
cout << fixed << setprecision(4) << rs;
}
int32_t main()
{
// freopen("248.in", "r", stdin);
// freopen("248.out", "w", stdout);
// turbo;
int tt = 1, j = 1;
// cin >> tt;
while (tt--)
{
// cout << "Case " << j << ":" << ew;
code();
// j++;
}
}
