#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 = 0;
    while (s) {
        if (s & 1)res++;
        s >>= 1;
    }
    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 = 0; i < N; i++) {
        if ((1 << i) & s)continue;
        int t = (1 << i) | s;
        if (vis[t])continue;
        vis[t] = 1;
        double sum = 0;
        for (int j = 0; j < N; j++)
            if ((1 << j) & s)
                sum += dis(i, j);
        dp[t] = dp[s] + sum;
        dfs(t);
    }
}

int main() {
    scanf("%d%d", &N, &M);
    for (int i = 0; i < N; i++)
        scanf("%lf%lf%lf", &L[i], &a[i], &b[i]);
    dfs(0);
    double ans = 0;
    for (int i = 0; i < (1 << N); i++)
        if (getOnes(i) == M)
            ans = max(ans, dp[i]);
    printf("%.5f\n", ans);
    return 0;
}