#include <cstdio>
#include <algorithm>
#include <limits>
#define repi(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,a) repi(i,0,a)
#define all(a) (a).begin(), (a).end()

constexpr int MAX_N = 5000;
using ll = long long;
constexpr ll INF = std::numeric_limits<ll>::max()>>2;

ll N, P;
ll a[3][MAX_N];
ll dp[2][15001];

void chmin( ll &a, ll b )
{ a = std::min( a, b ); }

int main()
{
  scanf( "%lld%lld", &N, &P );
  rep( i, N )
    scanf( "%lld%lld%lld", &a[0][i], &a[1][i], &a[2][i] );

  dp[0][P] = 0;

  rep( i, N )
  {
    rep( j, P+1 )
      dp[(i+1)%2][j] = INF;

    rep( j, P+1 )
    {
      rep( k, 4 ) if( j-k >= 0 )
        chmin( dp[(i+1)%2][j-k], dp[i%2][j]+(k==3?1:a[k][i]) );
    }
  }

  printf( "%lf\n", (double)dp[N%2][0]/N );
  
  return 0;
}