#include <iostream>
#include <iomanip>
using namespace std;

int main() {
    int n;
    cin >> n;
    
    double max_area = 0.0;
    
    for (int i = 0; i < n; ++i) {
        int a, b, h;
        cin >> a >> b >> h;
        
        double area = (a + b) * h / 2.0; // 计算当前梯形面积
        
        if (area > max_area) {
            max_area = area; // 更新最大面积
        }
    }
    
    cout << fixed << setprecision(1) << max_area << endl;
    
    return 0;
}

/**************************************************************
	Problem: 1330
	User: fuyijun
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/