破防了，遂刷一节课圆锥曲线放松大脑，原因如图

来个有缘人

#include<bits/stdc++.h>
using namespace std;
#define int __int128
void _print(__int128 x,bool first=true){if(x<0){putchar('-');_print(-x,false);return;}if(x==0){if(first) putchar('0');return;}_print(x/10,false);putchar((int)(x%10)+'0');
}
#define abs(x) (x>0?x:-x)
class frac{private:int z,m;public:frac(int x=0,int y=1){z=x,m=y;fixed();}frac fixed(){int gcd=__gcd(abs(z),abs(m));if(m<0){m*=-1;z*=-1;}if(z==0){m=1;return *this;}if(gcd==0) return *this;z/=gcd;m/=gcd;return *this;}frac upside(){return frac(m,z);}frac operator = (pair<int,int>A){z=A.first;m=A.second;fixed();return *this;}frac operator + (frac A){return (frac(z*A.m+m*A.z,m*A.m)).fixed();}frac operator * (frac A){// cout<<"multi ";this->print();putchar(' ');// A.print();putchar('=');int gcd1=__gcd(z,A.m);int gcd2=__gcd(A.z,m);frac ans=(frac((z/gcd1)*(A.z/gcd2),(m/gcd2)*(A.m/gcd1))).fixed();// ans.print();putchar('\n');return ans;}frac operator / (frac A){return (*this*A.upside()).fixed();}frac operator -(){return frac(-z,m);}frac operator -(frac A){return *this+(-A);}bool operator <(frac A){return z*A.m<A.z*m;}bool operator ==(frac A){return z*A.m==A.z*m;}bool operator >(frac A){return !(*this==A and *this<A);}void print(){fixed();_print(z);putchar('/');_print(m);// cout<<z<<"/"<<m<<endl;}frac _abs(){return frac(abs(z),abs(m));}long double it(){return z*1.0/m;}
};
struct node{signed x,y;
}p[1000001],s[1000001];
signed n;
double ans,mid;
double multi(node a1,node a2,node b1,node b2){return (a2.x-a1.x)*(b2.y-b1.y)-(b2.x-b1.x)*(a2.y-a1.y);
}
double dis(node p1,node p2){return sqrt((double)(p2.y-p1.y)*(p2.y-p1.y)*1.0+(double)(p2.x-p1.x)*(p2.x-p1.x)*1.0);
}
bool cmp(node p1,node p2){double tmp=multi(p[1],p1,p[1],p2);if(tmp>0) return true;if(tmp==0 and dis(p[0],p1)<dis(p[0],p2)) return true;return false;
}
int sqr_vector_dis(node a){return (__int128)a.x*a.x+(__int128)a.y*a.y;
}
int vector_multi(node a,node b){return abs((__int128)a.x*b.x+(__int128)a.y*b.y);
}
void print_node(node a){// cout<<"("<<a.x<<","<<a.y<<") ";
}
frac dist(node a,node b,node c){// cout<<"dist ";print_node(a);print_node(b);print_node(c);putchar(' ');//distance from c to line abnode vector1={b.x-a.x,b.y-a.y};node vector2={b.x-c.x,b.y-c.y};// cout<<"::";print_node(vector1);print_node(vector2);frac ans=frac(vector_multi(vector1,vector2)*vector_multi(vector1,vector2),sqr_vector_dis(vector1)*sqr_vector_dis(vector2));ans=-ans+1;ans=ans*sqr_vector_dis(vector2);ans=ans*frac(1,4);// cout<<"= ";ans.print();putchar('\n');return ans;
}
signed main(){freopen("a.in","r",stdin);freopen("a.out","w",stdout);scanf("%d",&n);for(int i=1;i<=n;++i){scanf("%d%d",&p[i].x,&p[i].y);if(i!=1 and p[i].y<p[1].y){mid=p[1].y;p[1].y=p[i].y;p[i].y=mid;mid=p[1].x;p[1].x=p[i].x;p[i].x=mid;}} sort(p+2,p+1+n,cmp);s[1]=p[1];int tot=1;for(int i=2;i<=n;i++){while(tot>1 and multi(s[tot-1],s[tot],s[tot],p[i])<=0) tot--;tot++;s[tot]=p[i];}s[tot+1]=p[1];int now=1;frac ans;for(int i=1;i<=tot;i++){//s[i] s[i+1]while(dist(s[i],s[i+1],s[now]).it()<dist(s[i],s[i+1],s[(now==tot?1:now+1)]).it()){now=(now==tot?1:now+1);}if(dist(s[i],s[i+1],s[now]).it()>ans.it()){ans=dist(s[i],s[i+1],s[now]);}}ans.print();
}