import logging
import sys
from inspect import currentframe

sys.setrecursionlimit(10 ** 6)
input = sys.stdin.readline

logging.basicConfig(level=logging.DEBUG)


def dbg(*args):
    id2names = {id(v): k for k, v in currentframe().f_back.f_locals.items()}
    logging.debug(
        ", ".join(id2names.get(id(arg), "???") + " = " + repr(arg) for arg in args)
    )


def main():

    INF = 10 ** 10
    n, p = map(int, input().split())
    a = [0] * n
    b = [0] * n
    c = [0] * n
    for i in range(n):
        a[i], b[i], c[i] = map(int, input().split())
    dp = [[INF] * (p + 1) for _ in range(n + 1)]
    dp[0][0] = 0
    for i in range(n):
        for j in range(p + 1):
            if j <= p:
                dp[i + 1][j] = min(dp[i][j] + a[i], dp[i + 1][j])
            if j + 1 <= p:
                dp[i + 1][j + 1] = min(dp[i][j] + b[i], dp[i + 1][j + 1])
            if j + 2 <= p:
                dp[i + 1][j + 2] = min(dp[i][j] + c[i], dp[i + 1][j + 2])
            if j + 3 <= p:
                dp[i + 1][j + 3] = min(dp[i][j] + 1, dp[i + 1][j + 3])
    # for i in range(n + 1):
    #     dbg(dp[i])
    ans = dp[n][p] / n
    print(ans)


if __name__ == "__main__":
    main()