#include <bits/stdc++.h>
using namespace std;

#define DUMP(x) cerr << #x << "=" << x << endl
#define DUMP2(x, y) cerr<<"("<<#x<<", "<<#y<<") = ("<<x<<", "<<y<<")"<< endl
#define BINARY(x) static_cast<bitset<16> >(x)

#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define REP(i,m,n) for (int i=m;i<(int)(n);i++)

#define in_range(x, y, w, h) (0<=(int)(x) && (int)(x)<(int)(w) && 0<=(int)(y) && (int)(y)<(int)(h))
#define ALL(a) (a).begin(),(a).end()

typedef long long ll;
const int INF   = 1e9;
const ll  INFLL = 1e18;
typedef pair<int, int> PII;
int dx[4]={0, -1, 1, 0}, dy[4]={-1, 0, 0, 1};

const int MAX_M = 15001;
ll dp[2][MAX_M];

int main()
{
    ios::sync_with_stdio(false);

    int N, P;
    cin >> N >> P;
    fill(dp[0], dp[0] + 2 * 15001, INFLL);
    dp[0][0] = 0;

    rep(i, N) {
        int A[4];
        rep(j, 3) cin >> A[j];
        A[3] = 1;

        fill(dp[(i+1)&1], dp[(i+1)&1] + 15001, INFLL);

        rep(j, MAX_M) { 
            rep(k, 4) {
                dp[(i+1)&1][j+k] = min(dp[(i+1)&1][j+k], dp[i&1][j] + A[k]);
            }
        }

#ifdef DEBUG
        DUMP(dp[(i+1)&1][0]);
#endif
    }

    cout << fixed << setprecision(10) << (dp[N&1][P] * 1.0 / N) << endl;
}