#include <stdio.h>
float ti(int a,int b,int c)
{
	return 1.0*(a+b)*c/2;
}
int main()
{
	int a[100][100];
    int n;
    float s=0;
    scanf("%d",&n);
    int i,j;
    for(i=0;i<n;i++){
    	for(j=0;j<3;j++){
    		scanf("%d",&a[i][j]);
		}
		if(s<ti(a[i][0],a[i][1],a[i][2])) s=ti(a[i][0],a[i][1],a[i][2]);
	}
	printf("%.1f",s);
    return 0;
}



/**************************************************************
	Problem: 1330
	User: admin
	Language: C
	Result: Accepted
	Time:9 ms
	Memory:1144 kb
****************************************************************/