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

#define REP(i, m, n) for (int i = (m); i < (int)(n); i++)
#define REPS(i, m, n) for (int i = (m); i <= (int)(n); i++)
#define rep(i, n) REP(i, 0, n)
#define reps(i, n) for (int i = 0; i <= (int)(n); i++)
#define rrep(i, x) for (int i = ((int)(x)-1); i >= 0; i--)
#define rreps(i, x) for (int i = (int)(x); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define pb push_back
typedef long long ll;
typedef pair<int, int> P;
const int inf = INT_MAX;
const ll INF = 1LL << 60;
const ll mod = 1e9 + 7;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<typename A, size_t N, typename T> void Fill(A (&array)[N], const T &val) { fill( (T*)array, (T*)(array+N), val ); }

double dp[5001][15001];
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N, P; cin >> N >> P;
    vector<int> a(N), b(N), c(N);
    rep(i, N) cin >> a[i] >> b[i] >> c[i];
    Fill(dp, 100000.0);
    rep(i, 4) dp[0][i] = 0;
    rep(i, N) reps(j, P) {
        if (abs(dp[i][j] - 100000) <= 0.01) continue;
        chmin(dp[i+1][j], ((dp[i][j] * i) + a[i]) / (i + 1));
        chmin(dp[i+1][j+1], ((dp[i][j] * i) + b[i]) / (i + 1));
        chmin(dp[i+1][j+2], ((dp[i][j] * i) + c[i]) / (i + 1));
        chmin(dp[i+1][j+3], ((dp[i][j] * i) + 1) / (i + 1));
    }
    printf("%.12lf\n", dp[N][P]);
    return 0;
}