#yuki_472

INF=float('inf')
n,p=map(int,raw_input().split())
dp = [INF for i in xrange(p+4)]
for i in xrange(n):
 a,b,c=map(int,raw_input().split())
 if i == 0:
  dp[0]=a
  dp[1]=b
  dp[2]=c
  dp[3]=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 1.0*dp[p]/n