#include <iostream>
#include <iomanip>

using namespace std;

int main() {
    int n;
    cin >> n;
    double maxArea = 0;
    for (int i = 0; i < n; ++i) {
        int a, b, h;
        cin >> a >> b >> h;
        double area = (a + b) * h / 2.0;
        if (area > maxArea) {
            maxArea = area;
        }
    }
    cout << fixed << setprecision(1) << maxArea << endl;
    return 0;
}
/**************************************************************
	Problem: 1330
	User: zhenghaoxuan
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/