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

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll, int> plli;
typedef pair<int, pii> pipii;
typedef vector<vector<int> > mati;
typedef vector<vector<double> > matd;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef vector<pll> vpll;

#define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
#define REP(i,y) FOR(i, 0, y)
#define RFOR(i,x,y) for(ll i=(ll)x; i>=(ll)y; --i)
#define RREP(i,x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back

inline void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

inline void OUT(void){
  cout << "\n";
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

template <typename T>
void vec_print(vector<T> VEC){
  REP(i, VEC.size()){
    cout << VEC[i] << " ";
  }
  cout << "\n";
};

template <typename T>
void mat_print(vector<vector<T> > MAT){
  REP(i, MAT.size()){
    REP(j, MAT[i].size()){
      cout << MAT[i][j] << " ";
    }
    cout << "\n";
  }
};

template <typename CLASS1, typename CLASS2>
class HOGE{
  public:
    CLASS1 key;
    CLASS2 value;
    HOGE(void){
      return;
    };
    HOGE(CLASS1 key, CLASS2 value){
      this->key = key;
      this->value = value;
    };
    ~HOGE(void){
      return;
    };

    void print(void){
      cout << "key : " << key << ", value : " << value << "\n";
      return;
    };
    
    bool operator==(const HOGE &obj){
      return (this->value == obj.value);
    };
    bool operator<(const HOGE &obj){
      return (this->value < obj.value);
    };
    bool operator>(const HOGE &obj){
      return (this->value > obj.value);
    };
};

template <typename CLASS1, typename CLASS2>
bool operator==(const HOGE<CLASS1, CLASS2> &hoge1, const HOGE<CLASS1, CLASS2> &hoge2){
  return hoge1.value == hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator<(const HOGE<CLASS1, CLASS2> &hoge1, const HOGE<CLASS1, CLASS2> &hoge2){
  return hoge1.value < hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator>(const HOGE<CLASS1, CLASS2> &hoge1, const HOGE<CLASS1, CLASS2> &hoge2){
  return hoge1.value > hoge2.value;
};

constexpr int INF = (1<<30);
constexpr ll INFLL = 1LL<<62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9)+7);

ll N;

ll calc1(const vpll& P){
  vector<pair<double, pair<ll, ll>>> P_tmp;
  ll x_pos = 0;
  ll y_pos = 0;
  REP(i,N){
    ll x = P[i].first;
    ll y = P[i].second;
    if(x>0){
      x_pos += x;
      y_pos += y;
      x = -x;
      y = -y;
    }
    double tmp = 0.0;
    if(x==0){
      if(y > 0){
        tmp = -(INFLL-1);
      }else{
        tmp = INFLL-1;
      }
    }else{
      tmp = (double)y/(double)x;
    }
    P_tmp.pb(make_pair(tmp, make_pair(x, y)));
  }
  ll ans = x_pos*x_pos + y_pos*y_pos;
  sort(ALL(P_tmp));
  REP(i,N){
    x_pos += P_tmp[i].second.first;
    y_pos += P_tmp[i].second.second;
    ans = max(ans, x_pos*x_pos+y_pos*y_pos);
  }
  return ans;
}

ll calc2(const vpll& P){
  vector<pair<double, pair<ll, ll>>> P_tmp;
  ll x_pos = 0;
  ll y_pos = 0;
  REP(i,N){
    ll x = P[i].first;
    ll y = P[i].second;
    if(x>0){
      x_pos += x;
      y_pos += y;
      x = -x;
      y = -y;
    }
    double tmp = 0.0;
    if(x==0){
      if(y > 0){
        tmp = -(INFLL-1);
      }else{
        tmp = INFLL-1;
      }
    }else{
      tmp = (double)y/(double)x;
    }
    P_tmp.pb(make_pair(tmp, make_pair(x, y)));
  }
  ll ans = x_pos*x_pos + y_pos*y_pos;
  sort(ALL(P_tmp));
  reverse(ALL(P_tmp));
  REP(i,N){
    x_pos += P_tmp[i].second.first;
    y_pos += P_tmp[i].second.second;
    ans = max(ans, x_pos*x_pos+y_pos*y_pos);
  }
  return ans;
}

ll calc3(const vpll& P){
  vector<pair<double, pair<ll, ll>>> P_tmp;
  ll x_pos = 0;
  ll y_pos = 0;
  REP(i,N){
    ll x = P[i].first;
    ll y = P[i].second;
    if(x<0){
      x_pos += x;
      y_pos += y;
      x = -x;
      y = -y;
    }
    double tmp = 0.0;
    if(x==0){
      if(y > 0){
        tmp = -(INFLL-1);
      }else{
        tmp = INFLL-1;
      }
    }else{
      tmp = (double)y/(double)x;
    }
    P_tmp.pb(make_pair(tmp, make_pair(x, y)));
  }
  ll ans = x_pos*x_pos + y_pos*y_pos;
  sort(ALL(P_tmp));
  REP(i,N){
    x_pos += P_tmp[i].second.first;
    y_pos += P_tmp[i].second.second;
    ans = max(ans, x_pos*x_pos+y_pos*y_pos);
  }
  return ans;
}

ll calc4(const vpll& P){
  vector<pair<double, pair<ll, ll>>> P_tmp;
  ll x_pos = 0;
  ll y_pos = 0;
  REP(i,N){
    ll x = P[i].first;
    ll y = P[i].second;
    if(x<0){
      x_pos += x;
      y_pos += y;
      x = -x;
      y = -y;
    }
    double tmp = 0.0;
    if(x==0){
      if(y > 0){
        tmp = -(INFLL-1);
      }else{
        tmp = INFLL-1;
      }
    }else{
      tmp = (double)y/(double)x;
    }
    P_tmp.pb(make_pair(tmp, make_pair(x, y)));
  }
  ll ans = x_pos*x_pos + y_pos*y_pos;
  sort(ALL(P_tmp));
  reverse(ALL(P_tmp));
  REP(i,N){
    x_pos += P_tmp[i].second.first;
    y_pos += P_tmp[i].second.second;
    ans = max(ans, x_pos*x_pos+y_pos*y_pos);
  }
  return ans;
}

int main(){
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after std::cin)
  ios::sync_with_stdio(false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  IN(N);
  vpll P(N);
  REP(i,N){
    IN(P[i].first, P[i].second);
  }

  sort(ALL(P));

  ll tmp1 = calc1(P);
  ll tmp2 = calc2(P);
  ll tmp3 = calc3(P);
  ll tmp4 = calc4(P);

  ll ans = max(max(tmp1, tmp2), max(tmp3, tmp4));
  printf("%.16lf\n", sqrt(ans));

  return 0;
}

Measured memory_bytes: 256