#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a[100][3];
	cin>>n;
	for(int i=0;i<n;i++){
		for(int j=0;j<3;j++) cin>>a[i][j];
	}
	float h=0;
	for(int i=0;i<n;i++){
		if(h){
			float l=0;
			l=(a[i][0]+a[i][1])*1.0*a[i][2]/2.0;
			h=max(l,h);
		}else{
			h=(a[i][0]+a[i][1])*1.0*a[i][2]/2.0;
		}
	}
    printf("%.1f",h);
}
/**************************************************************
	Problem: 1330
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/