#include <bits/stdc++.h>
using namespace std;
#define LD double//?????longdouble
const LD eps=1e-12;
const LD PI=acos(-1.0);
int sgn(LD x){return (x>eps)-(x<-eps);}
LD sqr(LD x){return x*x;}

LD rad_to_deg(LD r){return r*180.0/PI;}
LD deg_to_rad(LD r){return r*PI/180.0;}

struct PT
{
    LD x,y;
    PT(){x=0;y=0;}
    PT(LD x,LD y):x(x),y(y){}
    PT operator -(const PT &a)const {return PT(x-a.x,y-a.y);}
    PT operator +(const PT &a)const {return PT(x+a.x,y+a.y);}

    PT operator *(const LD a)const {return PT(x*a,y*a);}
    friend PT operator *(const LD &a,const PT &b){return PT(a*b.x,a*b.y);}
    PT operator /(const LD a)const {return PT(x/a,y/a);}

    PT perp(){return PT(-y,x);}//???90?
    LD arg(){return atan2(y,x); }//??(-pi,pi]
    LD norm(){return sqrt(x*x+y*y);}//?? 
    LD norm2(){return x*x+y*y;}//????
    PT truncate(LD r)//????r
    {
        LD k=norm();
        if(sgn(k)==0)return *this;
        r/=k;
        return PT(x*r,y*r);
    }
};
LD det(PT a,PT b){return a.x*b.y-a.y*b.x;}
LD dot(PT a,PT b){return a.x*b.x+a.y*b.y;}
LD Edis(PT a,PT b){return sqrt(sqr((a.x-b.x))+sqr((a.y-b.y)));}
LD Edis2(PT a,PT b){return sqr((a.x-b.x))+sqr((a.y-b.y));}
bool operator ==(PT a,PT b)
{
    return sgn(Edis2(a,b))==0;
}
int orientation(PT a, PT b, PT c) { return sgn(det(b-a,c-a));}
PT perp(PT a) { return PT(-a.y, a.x);}//???90
PT perp3(PT a) { return PT(a.y, -a.x); }//???90
PT rotatel(PT a, LD t) //???
{
    return PT(a.x*cos(t)-a.y*sin(t),a.x*sin(t)+a.y*cos(t));
}
PT rotater(PT a, LD t) //???
{
    return PT(a.x*cos(t)+a.y*sin(t),-a.x*sin(t)+a.y*cos(t));
}

LD get_angle(PT a,PT b)//?????
{
    return acos(max(-1.0,min(1.0,dot(a,b)/a.norm()/b.norm())));
}
PT midPT(PT a,PT b){return PT((a.x+b.x)/2.0,(a.y+b.y)/2.0);}//??

LD S(PT a,PT b,PT c)
{
    return abs(det(a-b,a-c));
}
LD S(vector<PT>&a)//????????
{
    if(a.size()<3)return 0;
    LD ans=0;
    for(int i=0;i<a.size();i++)ans+=det(a[i],a[(i+1)%a.size()]);
    return ans;
}
bool turn_left(PT a,PT b)//??b??????a??
{
    return sgn(det(a,b))>0;
}

vector<PT>get_convex(vector<PT>a)//??????a?????a?????
{
    if(a.size()<=2)return a;
    PT st=a[0];
    for(auto p:a)if(p.x<st.x||(p.x==st.x&&p.y<st.y))st=p;
    sort(a.begin(),a.end(),[&](PT u,PT v){
        int s=sgn(det(u-st,v-st));//1 ?v?u??
        return s!=0?s>0:Edis(u,st)<Edis(v,st);//????????
    });
    vector<PT>ret;ret.clear();
    for(auto p:a)
    {
        for(;ret.size()>1&&!turn_left(ret[ret.size()-1]-ret[ret.size()-2],p-ret[ret.size()-2]);)ret.pop_back();
        ret.push_back(p);
    }
    return ret;
}


const int N=5e5+3;
PT a[N<<1];
int main()
{
    int n;scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        a[i]=PT(x,y);
        a[i+n]=a[i];
    }

    LD ans=0;
    for(int l=1,r=2,mid=2;l<=n;l++,r++)
    {
        for(;mid<l+n&&sgn(S(a[l],a[r],a[mid+1])-S(a[l],a[r],a[mid]))>=0;mid++);
        ans=max(ans,max(Edis(a[l],a[mid]),Edis(a[r],a[mid])));
    }
    printf("%.10lf\n",ans);
    return 0;
}