from time import time
st = time()
N, P = map(int, input().split())
ABC = [list(map(int, input().split())) + [1] for _ in range(N)]
INF = 10 ** 9
dp = [0] * (P + 1)
cnt = 1
for A in ABC:
    cnt2 = min(cnt + 3, P + 1)
    for k in reversed(range(cnt2)):
        tmp = INF
        if 0 <= k < cnt:
            t1 = dp[k] + A[0]
            if tmp > t1:
                tmp = t1
        if 0 <= k - 1 < cnt:
            t1 = dp[k-1] + A[1]
            if tmp > t1:
                tmp = t1
        if 0 <= k - 2 < cnt:
            t1 = dp[k-2] + A[2]
            if tmp > t1:
                tmp = t1
        if 0 <= k - 3 < cnt:
            t1 = dp[k - 3] + A[3]
            if tmp > t1:
                tmp = t1

        dp[k] = tmp
    cnt = cnt2
#print(dp)
print(dp[P] / N)
print(time() - st)