#include<bits/stdc++.h>
using namespace std;
int main(){
	int c[5][5],n,d,g,a,i,j;
	float m=0,k=0;
	cin>>n;
for(i=0;i<n;i++) {
	for(j=0;j<3;j++) {
		cin>>c[i][j];
}
}
for(i=0;i<n;i++){
		k=(c[i][0]+c[i][1])*c[i][2]/2.0;
		if(m<k){
			m=k;
		}
}
printf("%.1f",m);

	return 0;
}

/**************************************************************
	Problem: 1330
	User: 12345678
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/