#include <bits/stdc++.h>
using namespace std;
int main()
{
    double n,a,b,h,s,maxx = 1.0;  
    cin >> n;
    for(int i = 1;i <= n;i++)
    {
        cin >> a >> b >> h;
        s = (a + b) * h / 2.0;
        maxx = max(maxx,s);  
    }
    cout << fixed << setprecision(1) << maxx;  
    return 0;
}