#include<iostream>
#include<algorithm>
using namespace std;
#define FOR(i, a, n) for(int i=a; i<n; i++)
#define RFOR(i, a, n) for(int i=n-1; i>=a; i--)
#define REP(i, n) FOR(i, 0, n)
#define RREP(i, n) RFOR(i, 0, n)
#define LL long long
#define INF 10000000

LL dp_from[15001];
LL dp_to[15001];
int main()
{
	int N, P;
	int a[5001], b[5001], c[5001];
	cin >> N >> P;
	REP(i, N) cin >> a[i] >> b[i] >> c[i];
	REP(i, 3 * N + 1) dp_from[i] = INF;

	dp_from[P] = 0;
	REP(i, N) {
		REP(j, 3 * N + 1) dp_to[j] = INF;
		REP(j, P + 1) {
			if (j >= 3) dp_to[j - 3] = min(dp_to[j - 3], dp_from[j] + 1);
			if (j >= 2) dp_to[j - 2] = min(dp_to[j - 2], dp_from[j] + c[i]);
			if (j >= 1) dp_to[j - 1] = min(dp_to[j - 1], dp_from[j] + b[i]);
			dp_to[j] = min(dp_to[j], dp_from[j] + a[i]);
		}
		swap(dp_from, dp_to);
	}

	printf("%.6lf\n", dp_from[0] * 1.0 / N);
	return 0;
}