fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

fn main() {
    let v:Vec<usize> = read_vec();
    let (n, p) = (v[0], v[1]);
    let mut a = vec![0i32; n];
    let mut b = vec![0i32; n];
    let mut c = vec![0i32; n];

    for i in 0..n {
        let v:Vec<i32> = read_vec();
        a[i] = v[0];
        b[i] = v[1];
        c[i] = v[2];
    }

    let mut dp = vec![vec![std::i32::MAX; p + 1]; n + 1];
    dp[0][0] = 0;

    for ni in 0..n {
        for pi in 0..p + 1{
            if dp[ni][pi] == std::i32::MAX {
                continue;
            }
            if pi + 0 <= p {
                dp[ni + 1][pi + 0] = std::cmp::min(dp[ni + 1][pi + 0], dp[ni][pi] + a[ni]);
            }
            if pi + 1 <= p {
                dp[ni + 1][pi + 1] = std::cmp::min(dp[ni + 1][pi + 1], dp[ni][pi] + b[ni]);
            }
            if pi + 2 <= p {
                dp[ni + 1][pi + 2] = std::cmp::min(dp[ni + 1][pi + 2], dp[ni][pi] + c[ni]);
            }
            if pi + 3 <= p {
                dp[ni + 1][pi + 3] = std::cmp::min(dp[ni + 1][pi + 3], dp[ni][pi] + 1);
            }
        }
    }
    // println!("{:?}", dp);
    println!("{:?}", dp[n][p] as f32 / n as f32);
}