#include<bits/stdc++.h>
using namespace std;
int main()
{
    int v[105][3];
    int n,a,b,h;
    float max=0,max_2;
    cin>>n;
    for(int i=0;i<n;i++){
        for(int j=0;j<3;j++){
            cin>>v[i][j];
         
        }
        a=v[i][0];
        b=v[i][1];
        h=v[i][2];
        max_2=((a+b)*h)/2.0;
        if(max<max_2)max=max_2;
    }
     
    printf("%.1f",max);
     
 
     
 
    return 0;
}
/**************************************************************
	Problem: 1330
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/