#include<bits/stdc++.h>
using namespace std;
struct  wsl {
    int a,b,c;
    float s;
}a[200];
bool cmp(wsl x,wsl 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].a>>a[i].b>>a[i].c;
   	a[i].s=(a[i].a+a[i].b)*a[i].c/2.0;
   }
   sort(a+1,a+1+n,cmp);
   printf("%.1f",a[1].s);
    return 0;
}
 
/**************************************************************
	Problem: 1330
	User: wangsenlin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2080 kb
****************************************************************/