#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i=0,j=0;
	float sun=0,d=0,a[100][3]={0};
	cin>>n;
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
		}
	}
	for(i=0;i<n;i++){
		sun=(a[i][0]+a[i][1])*a[i][2]/2;
		if(d<sun){
			d=sun;
		}
}
	printf("%.1f",d);
}
/**************************************************************
	Problem: 1330
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/