#include <bits/stdc++.h>

using namespace std;
ifstream fin ("mosia1.in");
ofstream fout ("mosia1.out");
const int Nmax = 205;
int n, st[Nmax], top;
double dp[Nmax];
struct P
{

    double ox, oy , dist;
};
P a[Nmax];
bool viz[Nmax];


inline bool CMP(const P A, const P B)
{
    if(A . oy == B . oy)
        return A . ox < B . ox;
    return A . oy < B . oy;
}
inline double CHECK(int i, int j, int k)
{
    return (a[i] . ox * a[j] . oy + a[i] . oy * a[k] . ox + a[j] . ox * a[k] . oy
            - a[k] . ox * a[j] . oy - a[j] . ox * a[i] . oy - a[i] . ox * a[k] . oy);
}
inline void Solve()
{
    ++top;
    st[1] = 1;
    ++top;
    st[top] = 2;
    viz[2] = true;
    for(int i = 3 ; i <= n ; i++)
    {
        while(top > 1 && CHECK(st[top - 1], st[top], i) < 0)
        {
            viz[st[top]] = false;
            top--;
        }
        ++top;
        st[top] = i;
        viz[i] = true;
    }
    for(int i = n ; i >= 1 ; i--)
        if(!viz[i]) /// nu se afla in infasuratoare
        {
            while(top > 1 && CHECK(st[top - 1], st[top], i) < 0)
            {
                viz[st[top]] = false;
                top--;
            }
            ++top;
            st[top] = i;
            viz[i] = true;
        }
    top--;
    ///for(int i = 1 ; i <= top ; i++)
        ///fout << st[i] << " ";
}
inline double Dist(int i , int j)
{
    return sqrt((a[j].ox - a[i] . ox) * (a[j].ox - a[i].ox) +
                (a[j].oy - a[i].oy) * (a[j].oy - a[i].oy));
}
inline void DP()
{
    /// dp[i] = aria maxima obtinuta din primele i
    /// alegand obligatoriu punctul st[1]
    double sol;
    dp[1] = Dist(st[n] , st[2]) * a[st[1]].dist / 2;
    dp[2] = dp[1];
    for(int i = 3 ; i < n ; i++)
    {
        dp[i] = max(dp[i - 1] , dp[i - 2] + Dist(st[i - 1] , st[i + 1]) * a[st[i]].dist / 2);
    }
    sol = dp[n - 1];
    /// dp[i] = aria maxima obtinuta din primele i
    /// alegand obligatoriu punctul st[2]
    dp[1] = 0;
    dp[2] = Dist(st[1] , st[3]) * a[st[2]].dist / 2;
    for(int i = 3 ; i <= n ; i++)
    {
        dp[i] = max(dp[i - 1] , dp[i - 2] + Dist(st[i - 1] , st[i + 1]) * a[st[i]].dist / 2);
    }
    sol = max(sol , dp[n]);
    fout << fixed << setprecision(6) <<  sol << "\n";
}
int main()
{
    fin >> n;
    for(int i = 1 ; i <= n ; i++)
        fin >> a[i] . ox >> a[i] . oy >> a[i] . dist;
    sort(a + 1, a + n + 1, CMP);
    Solve();
    DP();
    fin.close();
    fout.close();
    return 0;
}