#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

int n,p;
int a[5252],b[5252],c[5252];
int dp[2][15252];

int main(){
  scanf("%d%d",&n,&p);
  REP(i,n)scanf("%d%d%d",a+i,b+i,c+i);
  REP(i,3*n+1)REP(j,2)dp[j][i] = 1e9;
  int cur = 0;
  dp[cur][0] = 0;
  REP(i,n){
    int vs[4] = {a[i],b[i],c[i],1};
    REP(j,3*n+1)dp[cur^1][j] = 1e9;
    REP(j,3*n+1)REP(k,4){
      if(j+k<=3*n)CHMIN(dp[cur^1][j+k],dp[cur][j]+vs[k]);
    }
    // REP(j,3*n+1)DEBUG(dp[cur^1][j]);
    // puts("");
    cur ^= 1;
  }
  double ans = (double)dp[cur][p] / n;
  printf("%.10f\n",ans);
  return 0;
}