# -*- coding: utf-8 -*-

N, P = map(int, raw_input().split())

dp = [10**9 + 7]*(P + 5)
for i in xrange(N):
    a, b, c = map(int, raw_input().split())
    if i == 0:
        dp[:4] = [a, b, c, 1]
        continue
    for j in xrange(P, -1, -1):
        dp[j] = dp[j] + a
        if j > 0: dp[j] = min(dp[j], dp[j - 1] + b)
        if j > 1: dp[j] = min(dp[j], dp[j - 2] + c)
        if j > 2: dp[j] = min(dp[j], dp[j - 3] + 1)

print "%.10f" % (1.0*dp[P]/N)