#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a),i##END=(b);i<=i##END;i++)
#define Rof(i,b,a) for(int i=(b),i##END=(a);i>=i##END;i--)
#define go(u) for(int i=head[u];i;i=nxt[i])
#define int long long
using namespace std;
inline int read(){
    int 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<<1)+(x<<3)+(ch^48);ch=getchar();}
    return x*f;
}
const int N=2e6+10;
#define fi first
#define se second
int n,m,sum,c;
map<int,int> mp;
int val[N],id[N];
struct node{
	int x,y;
	int val(int a){return x*a+y;}
}q[N];int L,R;
bool check(node A,node B,node C){
	int x1=C.x-A.x,y1=C.y-A.y,x2=B.x-A.x,y2=B.y-A.y;
	return x1*x2+y1*y2>0; 
}
//bool check(node A,node B,node C){
//	return (B.y-A.y)*(C.x-B.x)>(C.y-B.y)*(B.x-A.x);
//}
signed main(){
	n=read(),mp[1]=0;
	For(i,1,n){
		int u=read(),v=read(),x=read();
		mp[u]+=x,mp[v]+=x,sum-=2*x;
	}for(auto x:mp)c++,id[c]=x.fi*2,sum+=2*x.se,val[c]=sum;
	int ans=-1e18;
//	For(i,1,c)For(j,i,c)ans=max(ans,val[i]+val[j]-id[i]*id[j]);
	L=1,R=0;For(i,1,c){
		ans=max(ans,2*val[i]-id[i]*id[i]);
		while(L<R&&q[L].val(-id[i])<=q[L+1].val(-id[i]))L++;
		if(L<=R)ans=max(ans,val[i]+q[L].val(-id[i]));
		node now=(node){id[i],val[i]};
		while(L<R&&!check(q[R-1],q[R],now))R--;
		q[++R]=now;
	}
	cout<<1.0*ans/4<<endl;
	return 0;
}