#include <bits/stdc++.h>
using namespace std;

#define maxn 1000005

typedef pair<double, int64_t> pdl;

pdl a[maxn];
double pre[maxn];

void solve(void) {
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
    sort(a + 1, a + n + 1);

    double ans = 0;
    for (int i = 1; i <= n; i++) pre[i] = pre[i - 1] + a[i].second;
    for (int i = 0, j = 0; i <= n; i++) {
        if (i < n && a[i + 1].first == 0) continue;
        double Sx = pre[n] - pre[i], x = (i < n ? 1 / a[i + 1].first : 0);
        while (j < i && a[j + 1].first < 1 && pre[j + 1] * (1 / (1 - a[j + 1].first)) <= Sx * x) j++;
        if (j > 0 && a[j].first < 1) ans = max(ans, Sx + pre[j] - max(Sx * x, pre[j] * (1 / (1 - a[j].first))));
        if (j < i && a[j + 1].first < 1)
            ans = max(ans, Sx + pre[j + 1] - max(Sx * x, pre[j + 1] * (1 / (1 - a[j + 1].first))));
    }
    cout << setprecision(10) << fixed << ans << endl;
    return;
}

int main() {
    ios::sync_with_stdio(false), cin.tie(nullptr);

    int _ = 1;
    while (_--) solve();

    return 0;
}