import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)
inf = 10 ** 9


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

dp = [0]
for _ in range(N):
    a, b, c = map(int, input().split())

    ndp = [inf] * (len(dp) + 3)
    for i in reversed(range(len(dp))):
        ndp[i + 3] = min(ndp[i + 3], dp[i] + 1)
        ndp[i + 2] = min(ndp[i + 2], dp[i] + c)
        ndp[i + 1] = min(ndp[i + 1], dp[i] + b)
        ndp[i + 0] = min(ndp[i + 0], dp[i] + a)

    dp = ndp

print("{:.12f}".format(dp[P] / N))