#include<iostream>
using namespace std;
int a[105][4];
int main()
{
    int i,n,m,j;
    float t1=0,s=0;
    cin>>n;
    for(i=1;i<=n;i++){
        for(j=1;j<=3;j++){
            cin>>a[i][j];
        }
        
    }
    for(i=1;i<=n;i++){
        t1=(a[i][1]+a[i][2])*a[i][3]/2.0;
        if(s<t1){
        	s=t1;
		}
    } 
    printf("%.1f",s) ;
    return 0;
}
/**************************************************************
	Problem: 1330
	User: xuanhua
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2076 kb
****************************************************************/