#include<bits/stdc++.h>
using namespace std;
struct tx{
	int sd;
	int xd;
	int h;
}a[110];
int n;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i].sd>>a[i].xd>>a[i].h;
	}
      for(int i=1;i<=n-1;i++){
        for(int j=1;j<=n-i;j++){
            if((a[j].sd+a[j].xd)*1.0*a[j].h/2<(a[j+1].sd+a[j+1].xd)*1.0*a[j+1].h/2){
                swap(a[j],a[j+1]);
            }
        }
    }
    for(int i=1;i<=n;i++){
		cout<<fixed<<setprecision(1)<<(a[i].sd+a[i].xd)*1.0*a[i].h/2;
		break;
	}

}

/**************************************************************
	Problem: 1330
	User: hongguangxi
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/