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

using ll = long long;

#define REP(i, n) for (int i = 0; i < n; i++)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define pb push_back
#define mp make_pair
#define fill(x, y) memset(x, y, sizeof(x))
#define even(x) x % 2 == 0
#define odd(x) x % 2 != 0
#define all(x) x.begin(), x.end()
#define pcnt __builtin_popcount
#define buli(x) __builtin_popcountll(x)
#define F first
#define S second
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

ll qp(ll a, ll b, int mo) { ll ans = 1; do { if (b & 1) ans = 1ll * ans * a % mo; a = 1ll * a * a % mo; } while (b >>= 1); return ans; }
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

template <typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }

template <typename T, typename... Ts>
auto make_v(size_t a, size_t b, Ts... ts) { return vector<decltype(make_v<T>(b, ts...))>(a, make_v<T>(b, ts...)); }
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type
fill_v(T &t, const V &v) { t = v; }
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type
fill_v(T &t, const V &v) { for (auto &e : t) fill_v(e, v); }
// auto dp = make_v<int>(4, h, w);
// fill_v(dp, 0);

const ll INF_LL = (1ll << 60);
const int INF_INT = (int)1e9;
const ll MOD_CONST = (ll)(1e9 + 7);

template <class T>
bool chmax(T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; }
template <class T>
bool chmin(T &a, const T &b) { if (b < a) { a = b; return 1; } return 0; }

inline tuple<ll, ll> rotate45(tuple<ll, ll> p) { ll x = get<0>(p), y = get<1>(p); return tuple<ll, ll>(x + y, x - y); }

int main(void)
{
	cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(20);

  int N, P; cin >> N >> P;
  auto abc = make_v<ll>(N, 3);
  REP(i, N) cin >> abc[i][0] >> abc[i][1] >> abc[i][2];
  
  auto dp = make_v<ll>(max(3, P+1));
  REP(i, 3) dp[i] = abc[0][i];
  FOR(i, 3, P+1) dp[i] = 1;

  vector<ll> cdp(dp.size());
  FOR(i, 1, N) {
    copy(all(dp), cdp.begin());
    FOR(j, 0, max(3, P+1)) {
      ll a = abc[i][0], b = abc[i][1], c = abc[i][2];
      ll v1 = min(cdp[j] + a, (j > 0) ? (cdp[j-1] + b) : INT64_MAX);
      ll v2 = min((j > 1) ? (cdp[j-2] + c) : INT64_MAX, (j > 2) ? (cdp[j-3] + 1) : INT64_MAX);
      dp[j] = min(v1, v2);
    }
  }
  
  cout << (double)dp[P] / (double)N << endl;

	return 0;
}