#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i,j,a[101][3];
	float s=0,max=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++){	
		s=(a[i][0]+a[i][1])*a[i][2]/2.0;
		if(s>max){
			max=s;
		}
		
	}
	printf("%.1f",max);
	
	
	
}
/**************************************************************
	Problem: 1330
	User: chenjunlin
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/