#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;

int n, p, dp[5005][15005];
const int INF = 1000000007;

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> n >> p;
	FOR(i, n+1) FOR(j, 3*n+1) dp[i][j] = INF;
	FOR(i, n) {
		int v[4];
		FOR(k, 3) cin >> v[k];
		v[3] = 1;
		if (i == 0) {
			FOR(k, 4) dp[i+1][k] = v[k];
		}
		else {
			FOR(j, p+1) {
				FOR(k, 4) {
					if (j+k <= p) dp[i+1][j+k] = min(dp[i+1][j+k], dp[i][j]+v[k]);
				}
			}
		}

	}
	printf("%.10lf\n", dp[n][p]/(double)n);
	return 0;
}