#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int (i)=(0);(i)<(int)(n);++(i))
using ll = long long;
//using P = pair<int, int>;
using namespace std;

template<class T> void vin(vector<T>& v, int n) {
    v.resize(n);
    for (int i = 0; i < n; ++i) {
        cin >> v[i];
    }
}

const int MAXN = 5010;
const int INF = 1e9;

int dp[MAXN][3*MAXN+1];
int N, P;
int a[MAXN], b[MAXN], c[MAXN];

int solve(int idx, int p) {
    int& res = dp[idx][p];
    if (res != INF) return res;
    if (idx >= N) {
        if (p > 0) res = 1e7;
        else if (p == 0) res = 0;
    }
    else {
        if (p >= 3) res = min(res, solve(idx+1, p-3) + 1);
        if (p >= 2) res = min(res, solve(idx+1, p-2) + c[idx]);
        if (p >= 1) res = min(res, solve(idx+1, p-1) + b[idx]);
        res = min(res, solve(idx+1, p) + a[idx]);
    }
    return res;
}

int main() {
    cin >> N >> P;
    fill(dp[0], dp[N], INF);
    rep(i, N) cin >> a[i] >> b[i] >> c[i];
    printf("%.10f\n", solve(0,P)*1.0/N);
    return 0;
}