//Shirasu Azusa 2024.7
#include <bits/stdc++.h>
#define fi first
#define se second
#define eb emplace_back
#define mp make_pair
using namespace std;
typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;
typedef __int128 i128;
template<class T,class S>
bool chmax(T &a,const S b) {return (a<b?a=b,1:0);}
template<class T,class S>
bool chmin(T &a,const S b) {return (a>b?a=b,1:0);}
int popcnt(int x) {return __builtin_popcount(x);}
int popcnt(ll x)  {return __builtin_popcountll(x);}
int topbit(int x) {return (x==0?-1:31-__builtin_clz(x));}
int topbit(ll x)  {return (x==0?-1:63-__builtin_clzll(x));}
int lowbit(int x) {return (x==0?-1:__builtin_ctz(x));}
int lowbit(ll x)  {return (x==0?-1:__builtin_ctzll(x));}

#define int long long
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int Vi=(a);i>=(b);i--)
typedef pair<int,int> pii;  
typedef vector<int> vi;
typedef vector<pii> vp;
typedef tuple<int,int,int> tiii;
int read() {
  int x=0,w=1; char c=getchar(); 
  while(!isdigit(c)) {if(c=='-') w=-1; c=getchar();}
  while(isdigit(c)) {x=x*10+(c-'0'); c=getchar();} 
  return x*w;
}

const ld eps=1e-11;
int cmp(ld a,ld b) { //a<b
  if(b-eps<=a&&a<=b+eps) return 0;
  else if(a<b) return 1; else return -1;
}
struct vec{ld x,y;};
ld operator ^ (vec a,vec b) {return a.x*b.y-a.y*b.x;}
vec operator - (vec a,vec b) {return (vec){a.x-b.x,a.y-b.y};}
ld dis(vec a,vec b) {return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}
ld area(vec a,vec b,vec c) {
  ld ans=(a-b)^(a-c);
  if(ans<0) ans=-ans; return ans;
}

signed main() {
  int n=read(); vector<vec> p(n);
  rep(i,0,n-1) p[i].x=read(), p[i].y=read(); ld ans=0;
  vector<vec> q; q.reserve(n);
  rep(i,0,n-1) {
    int x=(i+(n-1))%n, y=(i+1)%n;
    if(cmp((p[i]-p[x])^(p[i]-p[y]),0)) q.eb(p[i]);
    else if((p[i].x<p[x].x)==(p[i].x<p[y].x)) q.eb(p[i]);
  } swap(p,q);
  if(p.size()<=2) {
    printf("%.10Lf\n",dis(p[0],p[1]));
    return 0;
  }
  rep(i,0,n-1) {
    int x=(i+(n-1))%n, y=(i+1)%n;
    assert(cmp((p[i]-p[x])^(p[i]-p[y]),0));
  }
  for(int i=0,j=2;i<n;i++) {
    while(area(p[i],p[(i+1)%n],p[j])<=area(p[i],p[(i+1)%n],p[(j+1)%n])) j=(j+1)%n;
    chmax(ans,max(max(dis(p[i],p[j]),dis(p[i],p[(i+1)%n])),dis(p[j],p[(i+1)%n])));
  }
  printf("%.10Lf\n",ans);
  return 0;
}