#include<iostream>

#include<cstring>

#include<algorithm>

#include<cstdio>

#define MAX_N 20

#define MAX_S 1<<20

using namespace std;

double dp[MAX_S];

double L[MAX_N],a[MAX_N],b[MAX_N];

int N,M;

int getOnes(int s) {

    int res = ;

    while (s) {

        if (s & )res++;

        s >>= ;

    }

    return res;

}

bool vis[MAX_S];

double dis(int i,int j) {

    return (L[i] - L[j]) * (L[i] - L[j]) + (a[i] - a[j]) * (a[i] - a[j]) + (b[i] - b[j]) * (b[i] - b[j]);

}

void dfs(int s) {

    for (int i = ; i < N; i++) {

        if (( << i) & s)continue;

        int t = ( << i) | s;

        if (vis[t])continue;

        vis[t] = ;

        double sum = ;

        for (int j = ; j < N; j++)

            if (( << j) & s)

                sum += dis(i, j);

        dp[t] = dp[s] + sum;

        dfs(t);

    }

}

int main() {

    scanf("%d%d", &N, &M);

    for (int i = ; i < N; i++)

        scanf("%lf%lf%lf", &L[i], &a[i], &b[i]);

    dfs();

    double ans = ;

    for (int i = ; i < ( << N); i++)

        if (getOnes(i) == M)

            ans = max(ans, dp[i]);

    printf("%.5f\n", ans);

    return ;

}