//write by szh
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;

ll read()
{
	ll x=0,f=1;char ch=getchar();
	while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
	while (ch>='0'&&ch<='9'){x=x*10+ch-48;ch=getchar();}
	return x*f;
}
struct dian{
	ll x,y;
	long double tt;
}d[101];
long double ans=0,xx,yy;
bool cmp(dian a,dian b) {
	return a.tt<b.tt;
}
int main() {
	int n = read();
	for(int i=1;i<=n;i++) {
		d[i].x=read();
		d[i].y=read();
		d[i].tt=atan2(d[i].y,d[i].x);
	}
	sort(d+1,d+1+n,cmp);
	for (int i=1;i<=n;i++){
		xx=0,yy=0;
		for (int j=i;j<=n;j++){
			xx+=d[j].x;
			yy+=d[j].y;
			ans=max(ans,xx*xx+yy*yy); 
		}
	}
	printf("%.15Lf",sqrt(ans));
	return 0;
}