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

using ll = long long;
using ull = unsigned long long;
using ld = long double;
template<class t> using vc = vector<t>;
template<class t> using vvc = vc<vc<t>>;
using pi = pair<int,int>;
using pl = pair<ll,ll>;
using vi = vc<int>;
using vvi = vvc<int>;
using vl = vc<ll>;
using vvl = vvc<ll>;

#define rep(i,a,b) for (int i = (int)(a); i < (int)(b); i++)
#define irep(i,a,b) for (int i = (int)(a); i > (int)(b); i--)
#define all(a) a.begin(),a.end()
#define print(n) cout << n << '\n'
#define pritn(n) print(n)
#define printv(n,a) {copy(all(n),ostream_iterator<a>(cout," ")); cout<<"\n";}
#define printvv(n,a) {for(auto itr:n) printv(itr,a);}
#define rup(a,b) (a+b-1)/b
#define input(A,N) rep(i,0,N) cin>>A[i]
#define chmax(a,b) a = max(a,b)
#define chmin(a,b) a = min(a,b)


int main(){
    cout << fixed << setprecision(15);
    
    int n,p;
    cin>>n>>p;
    int inf = (int)1e8;
    vvi dp(n+1,vi(p+1,inf));
    dp[0][p] = 0;

    for(int i = 0;i<n;i++){
        int a,b,c;
        cin>>a>>b>>c;
        for(int j = 0;j<=p;j++){
            int ni = j;
            if(ni>=0) chmin(dp[i+1][ni],dp[i][j]+a);
            ni = j - 1;
            if(ni>=0) chmin(dp[i+1][ni],dp[i][j]+b);
            ni = j - 2;
            if(ni>=0) chmin(dp[i+1][ni],dp[i][j]+c);
            ni =  j - 3;
            if(ni>=0) chmin(dp[i+1][ni],dp[i][j]+1);
        }
    }
    print((double)dp[n][0]/(double)n);
    
    //system("pause");
    return 0;
}