#include<bits/stdc++.h>
using namespace std;
struct w{
    int sd;
    int xd;
    int g;
    float s;
}a[220];
bool cmp(w x,w y){
	if(x.s>y.s) return true;
	else return false;
}
int main(){
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i].sd>>a[i].xd>>a[i].g;
		a[i].s=(a[i].sd+a[i].xd)*a[i].g/2.0;
	}
	sort(a+1,a+1+n,cmp);
	printf("%.1f",a[1].s);
	return 0;
}
/**************************************************************
	Problem: 1330
	User: duyahan
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2080 kb
****************************************************************/