#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,a[100][3];
    cin>>n;
    for(int i=0;i<n;i++){
        for(int j=0;j<3;j++) cin>>a[i][j];
    }
    float h=0;
    for(int i=0;i<n;i++){
        if(h){
            float l=0;
            l=(a[i][0]+a[i][1])*1.0*a[i][2]/2.0;
            h=max(l,h);
        }else{
            h=(a[i][0]+a[i][1])*1.0*a[i][2]/2.0;
        }
    }
    printf("%.1f",h);
}
/**************************************************************
	Problem: 1330
	User: chenmingyu
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2076 kb
****************************************************************/