#include<bits/stdc++.h>
using namespace std;
struct  zal {
    int a,b,c;
    float s;   
}a[200];
bool cmp(zal x,zal 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)*1.0*a[i].c/2;
 
  }
    sort(a+1,a+1+n,cmp);
    printf("%.1f",a[1].s);
    return 0;
}
/**************************************************************
	Problem: 1330
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2080 kb
****************************************************************/