#include<iostream>
#include<cstring>
#include<vector>
#include<cmath>
#include<numeric>
#include<iomanip>
#include<algorithm>
using namespace std;
using LL = long long;

const int maxn = 1e5 + 5;
int tr[maxn];

int lowbit(int x){
    return x & -x;
}

void modify(int x, int v){
    while(x < maxn){
        tr[x] += v;
        x += lowbit(x);
    }
}

int query(int x){
    int ans = 0;
    while(x){
        ans += tr[x];
        x -= lowbit(x);
    }
    return ans;
}

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(20);

    int n;
    cin >> n;
    vector<pair<int, int> > p(n);
    for(int i = 0; i < n; i++){
        cin >> p[i].first >> p[i].second;
    }

    const double pi = numbers::pi;

    auto check = [&](double a){
        double cosa = cos(a), sina = sin(a);
        vector<pair<int, double> > pt(n);
        vector<double> nums;
        nums.reserve(n);
        for(int i = 0; i < n; i++){
            auto [x, y] = p[i];
            pt[i] = {y, x * sina + -y * cosa};
            nums.push_back(pt[i].second);
        }
        sort(nums.begin(), nums.end());
        nums.erase(unique(nums.begin(), nums.end()), nums.end());
        sort(pt.begin(), pt.end(), [&](auto &&a, auto &&b){
            if (a.first != b.first) return a.first > b.first;
            return a.second > b.second;
        });
        LL ans = 0;
        memset(tr, 0, sizeof tr);
        for(int i = 0; i < n; i++){
            auto [x, y] = pt[i];
            int t = lower_bound(nums.begin(), nums.end(), y) - nums.begin() + 1;
            ans += i - query(t - 1);
            modify(t, 1);
        }
        return ans;
    };

    auto get = [&](LL cnt){

        double l = 0, r = pi;
        for(int _ = 0; _ < 70; _++){
            double mid = (l + r) / 2;
            if (check(mid) >= cnt) r = mid;
            else l = mid;
        }
        return r;
    };

    LL tot = 1LL * n * (n - 1) / 2;
    if (tot % 2 == 1){
        cout << get(tot / 2 + 1) << '\n';
    }
    else{
        cout << (get(tot / 2) + get(tot / 2 + 1)) / 2 << '\n';
    }

}