#include "bits/stdc++.h"
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,x,n) for(int i=x;i<n;i++)
#define ALL(v) (v).begin(),(v).end()
#define MP(a,b) make_pair(a,b)
typedef long long LL;
typedef pair<int, int> PI;
typedef vector<int> VI;
const LL MOD = 1000000007LL;
int dp[15001];
int a[5000], b[5000], c[5000];
int main() {
	int N, P;
	cin >> N >> P;
	rep(i, N) {
		cin >> a[i] >> b[i] >> c[i];
	}
	fill(dp, dp + 15001, 1 << 30);
	dp[0] = 0;
	rep(i, N) {
		for (int j = P; j >= 0; j--) {
			int nxt = 1 << 30;
			if(dp[j]!=1<<30) nxt = min(nxt, dp[j] + a[i]);
			if (j >= 1 && dp[j-1]!=1<<30) nxt = min(nxt, dp[j - 1] + b[i]);
			if (j >= 2 && dp[j-2]!=1<<30) nxt = min(nxt, dp[j - 2] + c[i]);
			if (j >= 3 && dp[j-3]!=1<<30) nxt = min(nxt, dp[j - 3] + 1);
			dp[j] = nxt;
		}
	}
	printf("%.15lf\n", (double)dp[P] / N);
}