n, p = map(int, input().split())
dp = [1 << 30] * (p + 1)
dp[0] = 0
for _ in range(n):
    a, b, c = map(int, input().split())
    for i in range(p, -1, -1):
        mi = dp[i] + a
        if i >= 1:
            mi = min(mi, dp[i - 1] + b)
            if i >= 2:
                mi = min(mi, dp[i - 2] + c)
                if i >= 3:
                    mi = min(mi, dp[i - 3] + 1)
        dp[i] = mi

print(dp[-1] / n)