using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
using static Exg;
static class Program{
	const int mod=(int)1e9+7;
	static void Main(){
		Sc sc=new Sc();
		var n=sc.I;
		var pa=new Pair[n];
		for(int i = 0;i<n;i++) {
			pa[i]=new Pair(sc.Da);
		}
		var g=new Pair(0,0);
		var c=new Pair(0,0);
		double ans=0;
		var ca=Psort2(pa,new Pair(0,0));
		for(int i = 0;i<n;i++) {
			c=new Pair(0,0);
			for(int j = i;j<n+i;j++) {
				c+=ca[j].Item1;
				ans=Max(ans,Gp0(g,c));
			}
		}
		Console.WriteLine(ans);
	}
}
public struct Pair{
	public double x,y;
	public Pair(double x,double y){this.x=x;this.y=y;}
	public Pair(double[] da){x=da[0];y=da[1];}
	public Pair(Pair p){x=p.x;y=p.y;}
	public override string ToString()=>x.ToString()+" "+y.ToString();
	public static Pair operator+(Pair a,Pair b){a.x+=b.x;a.y+=b.y;return a;}
	public static Pair operator-(Pair a,Pair b){a.x-=b.x;a.y-=b.y;return a;}
	public static Pair operator*(Pair a,double n){a.x*=n;a.y*=n;return a;}
	public static Pair operator/(Pair a,double n){a.x/=n;a.y/=n;return a;}
}
static class Exg{
	static public double Gp0(Pair a,Pair b){return Sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}
	static public Tuple<bool,Pair> Gp1(Pair p1,Pair p2,Pair p3,Pair p4){
		double t1=(p4.y-p3.y)*(p4.x-p1.x)-(p4.x-p3.x)*(p4.y-p1.y);
		double t2=(p2.x-p1.x)*(p4.y-p1.y)-(p2.y-p1.y)*(p4.x-p1.x);
		double t3=(p2.x-p1.x)*(p4.y-p3.y)-(p2.y-p1.y)*(p4.x-p3.x);
		if(t3==0){
			if(Abs(Atan2(p2.y-p1.y,p2.x-p1.x))!=Abs(Atan2(p3.y-p1.y,p3.x-p1.x))){return Tuple.Create(p1.x==p3.x&&p1.y==p3.y?true:false,p1);}
			var a=new Tuple<Pair,int>[]{Tuple.Create(p1,1),Tuple.Create(p2,2),Tuple.Create(p3,3),Tuple.Create(p4,4)};
			Array.Sort(a,(d,e)=>{var c=d.Item1.x.CompareTo(e.Item1.y);return c==0?e.Item1.y.CompareTo(d.Item1.y):c;});
			return Tuple.Create((Abs(a[0].Item2-a[1].Item2)!=1||Abs(a[2].Item2-a[3].Item2)!=1)||(a[1].Item1.x==a[2].Item1.x&&a[1].Item1.y==a[2].Item1.y)?true:false,a[1].Item1);
		}
		double t4=t1/t3,t5=t2/t3;
		if(t4<0||t4>1||t5<0||t5>1){return Tuple.Create(false,new Pair(0,0));}
		else{return Tuple.Create(true,new Pair(p1.x+t4*(p2.x-p1.x),p1.y+t4*(p2.y-p1.y)));}
	}
	static public double Gp2(Pair p1,Pair p2,Pair p0){return Abs((p2.y-p1.y)*p0.x-(p2.x-p1.x)*p0.y+p2.x*p1.y-p1.x*p2.y)/Sqrt((p2.y-p1.y)*(p2.y-p1.y)+(p2.x-p1.x)*(p2.x-p1.x));}
	static public double Gp3(Pair p1,Pair p2,Pair p0){return (p1.x-p2.x)*(p0.y-p1.y)+(p1.y-p2.y)*(p1.x-p0.x);}
	static public double Gp4(Pair a,Pair b,Pair c){
		double a1=a.x-b.x,a2=a.y-b.y,c1=c.x-b.x,c2=c.y-b.y;
		return Acos((a1*c1+a2*c2)/Sqrt((a1*a1+a2*a2)*(c1*c1+c2*c2)))*180/PI;
	}
	static public Tuple<bool,Pair> Gp5(Pair p1,Pair p2,Pair p0){
		double rx=p0.x,ry=p0.y;
		if(p1.x==p2.x){rx=p1.x;}
		else if(p1.y==p2.y){ry=p1.y;}
		else{
			double m1=(p2.y-p1.y)/(p2.x-p1.x),b1=p1.y-(m1*p1.x),m2=-1.0/m1,b2=p0.y-(m2*p0.x);
			rx=(b2-b1)/(m1-m2);
			ry=(b2*m1-b1*m2)/(m1-m2);
		}
		return Tuple.Create(((p1.x>=rx&&p2.x<=rx)||(p2.x>=rx&&p1.x<=rx))&&((p1.y>=ry&&p2.y<=ry)||(p2.y>=ry&&p1.y<=ry)),new Pair(rx,ry));
	}
	static public Pair Gp6(Pair a,Pair b,Pair c,int n){
		double l1=Sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
		double l2=Sqrt((c.x-b.x)*(c.x-b.x)+(c.y-b.y)*(c.y-b.y));
		double ex=(a.x+(b.x+(c.x-b.x)*(l1/l2)))/2,ey=(a.y+(b.y+(c.y-b.y)*(l1/l2)))/2;
		ex+=(ex-b.x)*n;ey+=(ey-b.y)*n;
		return new Pair(ex,ey);
	}
	static public Pair Gp7(Pair a,double k,double p){return new Pair(a.x+k*Cos(p),a.y+k*Sin(p));}
	static public bool Gp8(Pair a,Pair b,Pair c){return (c.x-a.x)*(b.y-a.y)==(b.x-a.x)*(c.y-a.y);}
	static public Tuple<Pair,double>[] Psort(Pair[] pa,Pair p){
		var arr=new Tuple<Pair,double>[pa.Length];
		for(int i = 0;i<pa.Length;i++) {arr[i]=Tuple.Create(pa[i],Atan2(pa[i].y-p.y,pa[i].x-p.x)*180/PI+180);}
		Array.Sort(arr,(u,v)=>u.Item2.CompareTo(v.Item2));
		return arr;
	}
	static public Tuple<Pair,double>[] Psort2(Pair[] pa,Pair p){
		int n=pa.Length;
		var arr=new Tuple<Pair,double>[n];
		for(int i = 0;i<n;i++) {arr[i]=Tuple.Create(pa[i],Atan2(pa[i].y-p.y,pa[i].x-p.x)*180/PI+180);}
		Array.Sort(arr,(u,v)=>u.Item2.CompareTo(v.Item2));
		Array.Resize(ref arr,n<<1);
		for(int i = 0;i<n;i++) {arr[i+n]=Tuple.Create(arr[i].Item1,arr[i].Item2+360);}
		return arr;
	}
}
public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),int.Parse);}
	public int[] Ia3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),long.Parse);}
	public long[] La3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),long.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}

Measured memory_bytes: 13268