/*?? - ??(13.7) ????   
 ?? POJ 2693?PG1009 
?? 
?????(x,y)????????????????
 ???? 
??????n?n????2? 
?????????????????x y???
 ???? 
??????????????? 
 ???? 
6
34.0 23.0
28.1 21.6
14.7 17.1
17.0 27.2
34.7 67.1
29.3 65.1
 ???? 
53.8516
 ?? 
????????????double???????? 
??printf("%.4f\n", dis)?????????????4?? 
*/
void main()
{
	int n,i,j;
	double max,a;
	double x[10],y[10],s[10];
	double f(double,double,double,double);
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		scanf("%lf%lf",&x[i],&y[i]);
	}
	for(i=0;i<n-1;i++)
	{
		s[i]=f(x[i],y[i],x[i+1],y[i+1]);
		if(i<n-2)
		{
		for(j=i+2;j<n;j++)
		{
			a=f(x[i],y[i],x[j],y[j]);
			if(s[i]<a)
				s[i]=a;
		}}
	}
	max=s[0];
	for(i=1;i<n;i++)
	{
		if(max<s[i])
			max=s[i];
	}
	printf("%.4f\n", max);
}
				
double f(double x1,double y1,double x2,double y2)
{
	double z;
	z=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
	return z;
}
