#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
#include <deque>
#include <iomanip>
#include <limits>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;
int dp[5005][15005]; // := i+1日めで正解数がjの時の順位の和の最小
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  int N, P; cin >> N >> P;
  FOR(i,0,N+1) FOR(j,0,15005) dp[i][j] = 2e9;
  dp[0][0] = 0;
  int a[N], b[N], c[N];
  FOR(i,0,N) cin >> a[i] >> b[i] >> c[i];
  FOR(i,0,N) {
    FOR(j,0,P+1) {
      // 0問
      dp[i+1][j] = min(dp[i+1][j], dp[i][j] + a[i]); 
      // 1問
      if(j+1<=P) dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j] + b[i]);
      // 2問
      if(j+2<=P) dp[i+1][j+2] = min(dp[i+1][j+2], dp[i][j] + c[i]);
      // 3問
      if(j+3<=P) dp[i+1][j+3] = min(dp[i+1][j+3], dp[i][j] + 1);
    }
  }
  cout << fixed << setprecision(17) << (double)dp[N][P] / N << endl;
  return 0;
}