#include<bits/stdc++.h>
using namespace std;
int main(){
    int a,b,h,n;
    float d=0,s=0;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>a>>b>>h;
        s=(a+b)*h/2.0;
        if(s>d){
            d=s;
        }
    }
    printf("%.1f",d);
} 
/**************************************************************
	Problem: 1330
	User: 12345678
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/