#!/usr/bin/env python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import numpy as np

N, P = map(int,readline().split())
m = map(int, read().split())
ABC = zip(m, m, m)

INF = 10 ** 9
dp = np.zeros(1, np.int32)
for a, b, c in ABC:
    n = len(dp)
    newdp = np.full(n + 3, INF, np.int32)
    newdp[3:] = dp + 1
    np.minimum(newdp[0:n], dp + a, out=newdp[0:n])
    np.minimum(newdp[1:n+1], dp + b, out=newdp[1:n+1])
    np.minimum(newdp[2: n + 2], dp + c, out=newdp[2: n + 2])
    dp = newdp

print(dp[P] / N)