import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val (N, P) = Pair(sc.nextInt(), sc.nextInt())
    val q = Array(N, { arrayOf(sc.nextInt(), sc.nextInt(), sc.nextInt() )})
    val inf = 100000L*N
    val dp = Array(P+4, { i -> if (i == 3) 0L else inf })
    for (i in 0 until N) {
        for (dest in Math.min(3*i+6, P+3) downTo 3) {
            dp[dest] = arrayOf(dp[dest]+q[i][0], dp[dest-1]+q[i][1], dp[dest-2]+q[i][2], dp[dest-3]+1).min()!!
        }
    }
    println(dp[P+3].toDouble() / N.toDouble())
}