#include<bits/stdc++.h>
using namespace std;
struct tx{
	int a,b,h;
	float s;
}a[200];
bool cmp(tx x,tx y){
	 if(x.s>y.s) return true;
	 return false;
}
int main(){
    int n;
    cin>>n;
    for(int i=1;i<=n;i++){
    	cin>>a[i].a>>a[i].b>>a[i].h;
    	a[i].s=(a[i].a+a[i].b)*1.0*a[i].h/2;
    }
    sort(a+1,a+1+n,cmp);
    printf("%.1f\n",a[1].s);
	return 0;
}

/**************************************************************
	Problem: 1330
	User: houlingqi2
	Language: C++
	Result: Accepted
	Time:21 ms
	Memory:2080 kb
****************************************************************/