#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: wengsihan
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/