#include <bits/stdc++.h>
using namespace std;
const int buff = 100000;
const long double dick = 1.0;
long long A[100008], B[100008];
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; long double x; cin >> n;
cout << fixed << setprecision(4);
for (int i = 1; i <= n; ++i) {
cin >> x; A[i] = round(x * buff);
cin >> x; B[i] = round(x * buff);
}
sort(A + 1, A + n + 1, greater<long long>()); sort(B + 1, B + n + 1, greater<long long>());
for (int i = 1; i <= n; ++i) A[i] += A[i - 1];
for (int i = 1; i <= n; ++i) B[i] += B[i - 1];
int j; long double ans = 0;
for (int i = 1; i <= n && A[i] <= B[n]; ++i) { // A[i] <= B[j]
j = lower_bound(B + 1, B + n + 1, A[i]) - B;
// cout << (A[i] * dick) / buff - i - j << '\n';
ans = max(ans, (A[i] * dick) / buff - i - j);
}
for (int i = 1; i <= n && B[i] <= A[n]; ++i) { // B[i] <= A[j]
j = lower_bound(A + 1, A + n + 1, B[i]) - A;
ans = max(ans, (B[i] * dick) / buff - i - j);
// cout << (B[i] * dick) / buff - i - j << '\n';
}
cout << ans;
}
