fn main(){
    let mut sc = Scanner::new();
    use std::cmp::min;
    while !sc.eof() {
        let n = sc.next();
        let p:usize = sc.next();
        let mut dp = [i32::max_value()/2; 15010];
        dp[0] = 0;
        for _ in 0..n {
            let a:i32 = sc.next();
            let b:i32 = sc.next();
            let c:i32 = sc.next();
            let mut ndp = [i32::max_value()/2; 15010];
            for j in 0..(3*n+1) {
                if j >= 0 { ndp[j] = min(ndp[j], dp[j-0] + a) }
                if j >= 1 { ndp[j] = min(ndp[j], dp[j-1] + b); }
                if j >= 2 { ndp[j] = min(ndp[j], dp[j-2] + c) }
                if j >= 3 { ndp[j] = min(ndp[j], dp[j-3] + 1) }
            }
            dp = ndp;
        }
        println!("{:.10}", dp[p] as f64 / n as f64);
    }
}

// Scanner
#[allow(dead_code)]
struct Scanner { token_buffer: Vec<String>, index: usize }

#[allow(dead_code)]
impl Scanner {
    fn new() -> Scanner {
        Scanner { token_buffer: vec![], index: 0 }
    }

    fn next<T>(&mut self) -> T where T: std::str::FromStr {
        self.wrapped::<T>().unwrap()
    }

    fn wrapped<T>(&mut self) -> Option<T> where T: std::str::FromStr {
        match self.get_token() {
            Some(s) => {
                match s.parse::<T>() {
                    Ok(x) => Some(x),
                    Err(_) => None
                }
            },
            None => None
        }
    }

    fn eof(&mut self) -> bool {
        if !self.read_line() {
            true
        } else {
            self.index >= self.token_buffer.len()
        }
    }

    fn get_token(&mut self) -> Option<&String> {
        if !self.read_line() {
            None
        } else {
            self.index += 1;
            Some(&self.token_buffer[self.index - 1])
        }
    }

    fn read_line(&mut self) -> bool {
        while self.index >= self.token_buffer.len() {
            let mut st = String::new();
            while st.trim() == "" {
                match std::io::stdin().read_line(&mut st) {
                    Ok(l) if l > 0 => continue,
                    _ => return false
                }
            }
            self.token_buffer = st.split_whitespace()
                .map(|x| x.to_string())
                .collect();
            self.index = 0;
        }
        true
    }
}