#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,i,a[100][100]={0},j;
    float m=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++){
        for(j=0;j<3;j++){
            m=(a[i][0]+a[i][1]) *a[i][2]/2.0;
            if(m>max){
                max=m;
            }
        }
    }
    printf("%.1f",max);
}
/**************************************************************
	Problem: 1330
	User: panjinyan
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/