#include <bits/stdc++.h>
//#define int long long

using namespace std;
using LL = long long;
using P = pair<int, int>;
using Tapris = tuple<int, int, int>;

#define FOR(i, a, n) for(int i = (int)(a); i < (int)(n); ++i)
#define REP(i, n) FOR(i, 0, n)

#define pb(a) push_back(a)
#define all(x) (x).begin(),(x).end()

const int INF = (int)1e9;
const LL INFL = (LL)1e15;
const int MOD = 1e9 + 7;

int dy[]={0, 0, 1, -1, 0};
int dx[]={1, -1, 0, 0, 0};

/*************** using variables ***************/
int n, p;
int a[5005][4];
int dp[15005];
/**********************************************/

signed main(){
    cin >> n >> p;
    REP(i, n) cin >> a[i][0] >> a[i][1] >> a[i][2], a[i][3] = 1;

    REP(i, n+1) dp[i] = INF;
    dp[0] = a[0][0];
    dp[1] = a[0][1];
    dp[2] = a[0][2];
    dp[3] = 1;

    FOR(i, 1, n){
        int tmp[15005];
        for(int j = 0; j <= p; j++){
            int min_num = INF;
            REP(k, 4){
                if(j >= k){
                    min_num = min(min_num, a[i][k] + dp[j-k]);
                }
            }
            tmp[j] = min_num;
        }
        for(int j = 0; j <= p; j++) dp[j] = tmp[j];
    }
    
    printf("%.9f\n" ,(double)dp[p] / n);
}