n, p = map(int, input().split())
dp = [[10**9] * (p + 1) for i in range(n + 1)]
dp[0][0] = 0
for i in range(n):
    a, b, c = map(int, input().split())
    for j in range(p + 1):
        dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + a)
        if j < p:
            dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j] + b)
        if j + 1 < p:
            dp[i + 1][j + 2] = min(dp[i + 1][j + 2], dp[i][j] + c)
        if j + 2 < p:
            dp[i + 1][j + 3] = min(dp[i + 1][j + 3], dp[i][j] + 1)
print(float(dp[n][p]) / float(n))