N, P = map(int, input().split())
contests = [list(map(int, input().split())) for _ in range(N)]
dp = [[float('inf')] * (P + 1) for _ in range(N + 1)]
dp[0][0] = 0
for i in range(N):
  a = contests[i]
  for j in range(P + 1):
    for k in range(3, -1, -1):
      if k < 3:
        add = a[k]
      else:
        add = 1
      if j + k <= P:
        dp[i + 1][j + k] = min(dp[i + 1][j + k], dp[i][j] + add)
#print(*dp, sep='\n')
print(dp[N][P] / N)