// Slower C++ solution:
#include <bits/stdc++.h>

typedef long long ll;

#define pb push_back

using namespace std;

typedef pair<ll,ll> pll;

typedef long double ld;





ll n;

vector< pll > v;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

inline ll f(ll X, ll Y)

{

        return (X*X + Y*Y);

}

int main()

{

        ios_base::sync_with_stdio(false);

        cin.tie(NULL); cout.tie(NULL);

        cout << setprecision(12) << fixed;

        cin >> n;

        ll ans = 0;

        ll X = 0;

        ll Y = 0;

        for(ll i=0;i<n;i++) {

                ll u,vv;

                cin >> u >> vv;

                v.pb(make_pair(u, vv));

                X += u;

                Y += vv;

                ans = max(ans , f(X, Y));

        }

        ll itr = 100005;

        while(itr--){

                X=0; Y=0;

                shuffle(v.begin(), v.end(), rng);

                for(ll i=0;i<n;i++){

                        //X += v[i].first; Y += v[i].second;

                        //ans=max(ans, f(X, Y));

                        if(f(X+v[i].first , Y + v[i].second) > f(X , Y)) {

                                X += v[i].first; Y += v[i].second;

                        }

                        ans= max(ans, f(X, Y));

                }

        }

        ld aa = 1.0*ans; aa = (ld)sqrt(aa);

        cout << aa << endl;

        return 0;

}


// Faster C++ solution for the same problem (measured speedup: 6.115779688401771x):
#include <bits/stdc++.h>

typedef long long ll;

#define pb push_back

using namespace std;

typedef pair<ll,ll> pll;

typedef long double ld;





ll n;

vector< pll > v;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

inline ll f(ll X, ll Y)

{

        return (X*X + Y*Y);

}

ld g(pll X, pll Y)

{

        if(Y.first == 0 && Y.second == 0) return 0;

        ld m1 = f(X.first, X.second);

        ld m2 = f(Y.first, Y.second);

        return (ld)(((ld)(X.first*Y.first + X.second*Y.second)) / (m1 * m2));

}

int main()

{

        ios_base::sync_with_stdio(false);

        cin.tie(NULL); cout.tie(NULL);

        cout << setprecision(12) << fixed;

        cin >> n;

        ll ans = 0;

        ll X=0; ll Y=0;

        for(ll i=0;i<n;i++) {

                ll u,vv;

                cin >> u >> vv;

                v.pb(make_pair(u, vv));

                X += u;

                Y += vv;

                ans = max(ans , f(X, Y));

        }

        for(ll i=0;i<n;i++) {

                pll A = v[i];

                if(A.first==0 && A.second == 0) continue;

                vector< pair<ld, ll> > t;

                for(ll j=0;j<n;j++) {

                        t.pb(make_pair(g(A, v[j]), j));

                }

                sort(t.rbegin(), t.rend());

                ll X = 0;

                ll Y = 0;

                for(auto &j : t){

                        ll id = j.second;

                        if(f(X + v[id].first, Y + v[id].second) > f(X , Y)) {

                                X += v[id].first; Y += v[id].second;

                        }

                        ans = max(ans, f(X , Y));

                }

        }

        ld aa = ans; aa = sqrt(aa);

        cout << aa << endl;

        return 0;

}