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())})
    var dp = Array(P+1, { 0L })
    val inf = 100000L*N
    val filled_dp = Array(P+1, { inf })
    for (i in 0 until N) {
        val _dp = filled_dp.clone()
        for (k in Math.min(3*(i+1), P) downTo 3) {
            println(k)
            _dp[k] = arrayOf(dp[k]+q[i][0], dp[k-1]+q[i][1], dp[k-2]+q[i][2], dp[k-3]+1L).min()!!
        }
        if (P >= 2) _dp[2] = arrayOf(dp[2]+q[i][0], dp[1]+q[i][1], dp[0]+q[i][2]).min()!!
        if (P >= 1) _dp[1] = Math.min(dp[1]+q[i][0], dp[0]+q[i][1])
        _dp[0] = dp[0]+q[i][0]
        dp = _dp
    }
    println(dp[P].toDouble() / N.toDouble())
}