#include<bits/stdc++.h>
using namespace std;
struct ss{
    int a,b,h;
    float s;
}m[100];
int main()
{
    int i,n;
    float max=0;
    cin>>n;
    for(i=0;i<n;i++){
        cin>>m[i].a>>m[i].b>>m[i].h;
        m[i].s=(m[i].a+m[i].b)*m[i].h/2.0;
        if(m[i].s>max)
            max=m[i].s; 
    }
    printf("%.1f",max);
}
/**************************************************************
	Problem: 1330
	User: chenjiahui
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/