/**
 *  _           _                 __                            _   _ _   _                                 _                    _                  _
 * | |         | |               / /                           | | (_) | (_)                               | |                  (_)                | |
 * | |__   __ _| |_ ___   ___   / /__ ___  _ __ ___  _ __   ___| |_ _| |_ ___   _____ ______ _ __ _   _ ___| |_ ______ ___ _ __  _ _ __  _ __   ___| |_ ___
 * | '_ \ / _` | __/ _ \ / _ \ / / __/ _ \| '_ ` _ \| '_ \ / _ \ __| | __| \ \ / / _ \______| '__| | | / __| __|______/ __| '_ \| | '_ \| '_ \ / _ \ __/ __|
 * | | | | (_| | || (_) | (_) / / (_| (_) | | | | | | |_) |  __/ |_| | |_| |\ V /  __/      | |  | |_| \__ \ |_       \__ \ | | | | |_) | |_) |  __/ |_\__ \
 * |_| |_|\__,_|\__\___/ \___/_/ \___\___/|_| |_| |_| .__/ \___|\__|_|\__|_| \_/ \___|      |_|   \__,_|___/\__|      |___/_| |_|_| .__/| .__/ \___|\__|___/
 *                                                  | |                                                                           | |   | |
 *                                                  |_|                                                                           |_|   |_|
 *
 * https://github.com/hatoo/competitive-rust-snippets
 */
#[allow(unused_imports)]
use std::cmp::{max, min, Ordering};
#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
#[allow(unused_imports)]
use std::iter::FromIterator;
#[allow(unused_imports)]
use std::io::{stdin, stdout, BufWriter, Write};
mod util {
    use std::io::{stdin, stdout, BufWriter, StdoutLock};
    use std::str::FromStr;
    use std::fmt::Debug;
    #[allow(dead_code)]
    pub fn line() -> String {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.trim().to_string()
    }
    #[allow(dead_code)]
    pub fn chars() -> Vec<char> {
        line().chars().collect()
    }
    #[allow(dead_code)]
    pub fn gets<T: FromStr>() -> Vec<T>
    where
        <T as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.split_whitespace()
            .map(|t| t.parse().unwrap())
            .collect()
    }
    #[allow(dead_code)]
    pub fn with_bufwriter<F: FnOnce(BufWriter<StdoutLock>) -> ()>(f: F) {
        let out = stdout();
        let writer = BufWriter::new(out.lock());
        f(writer)
    }
}
#[allow(unused_macros)]
macro_rules ! get { ( $ t : ty ) => { { let mut line : String = String :: new ( ) ; stdin ( ) . read_line ( & mut line ) . unwrap ( ) ; line . trim ( ) . parse ::<$ t > ( ) . unwrap ( ) } } ; ( $ ( $ t : ty ) ,* ) => { { let mut line : String = String :: new ( ) ; stdin ( ) . read_line ( & mut line ) . unwrap ( ) ; let mut iter = line . split_whitespace ( ) ; ( $ ( iter . next ( ) . unwrap ( ) . parse ::<$ t > ( ) . unwrap ( ) , ) * ) } } ; ( $ t : ty ; $ n : expr ) => { ( 0 ..$ n ) . map ( | _ | get ! ( $ t ) ) . collect ::< Vec < _ >> ( ) } ; ( $ ( $ t : ty ) ,*; $ n : expr ) => { ( 0 ..$ n ) . map ( | _ | get ! ( $ ( $ t ) ,* ) ) . collect ::< Vec < _ >> ( ) } ; ( $ t : ty ;; ) => { { let mut line : String = String :: new ( ) ; stdin ( ) . read_line ( & mut line ) . unwrap ( ) ; line . split_whitespace ( ) . map ( | t | t . parse ::<$ t > ( ) . unwrap ( ) ) . collect ::< Vec < _ >> ( ) } } ; ( $ t : ty ;; $ n : expr ) => { ( 0 ..$ n ) . map ( | _ | get ! ( $ t ;; ) ) . collect ::< Vec < _ >> ( ) } ; }
#[allow(unused_macros)]
macro_rules ! debug { ( $ ( $ a : expr ) ,* ) => { println ! ( concat ! ( $ ( stringify ! ( $ a ) , " = {:?}, " ) ,* ) , $ ( $ a ) ,* ) ; } }

#[allow(dead_code)]
pub const INF: u64 = 1 << 30;

#[allow(dead_code)]
fn main() {
    loop {
        let (n, m) = get!(usize, usize);
        if n == 0 && m == 0 {
            break;
        }
        let rows: Vec<Vec<usize>> = (0..n).map(|_| util::gets()).collect();

        let mut dp = vec![vec![vec![INF; m + 1]; 1001]; n];

        for i in 0..n {
            for v in rows[i][1..].chunks(2) {
                let r = v[0];
                let cost = v[1] as u64;

                for j in 0..m + 1 {
                    if i == 0 {
                        dp[i][r][j] = 0;
                    } else {
                        for v2 in rows[i - 1][1..].chunks(2) {
                            let r1 = v2[0];
                            let cost1 = v2[1] as u64;

                            let mov = (r1 as isize - r as isize).abs() as u64;
                            let c = cost + cost1;
                            dp[i][r][j] = min(dp[i][r][j], dp[i - 1][r1][j] + mov * c);
                        }

                        if i >= 2 && j > 0 {
                            for v2 in rows[i - 2][1..].chunks(2) {
                                let r1 = v2[0];
                                let cost1 = v2[1] as u64;

                                let mov = (r1 as isize - r as isize).abs() as u64;
                                let c = cost + cost1;
                                dp[i][r][j] = min(dp[i][r][j], dp[i - 2][r1][j - 1] + mov * c);
                            }
                        }
                    }
                }

                if i == 1 {
                    for j in 1..m + 1 {
                        dp[i][r][j] = 0;
                    }
                }
                // debug!(i, r, dp[i][r]);
            }
        }

        let mut ans = INF;

        for i in 0..1001 {
            for j in 0..m + 1 {
                ans = min(ans, dp[n - 1][i][j]);
            }
        }

        for i in 0..1001 {
            for j in 0..m {
                ans = min(ans, dp[n - 2][i][j]);
            }
        }

        println!("{}", ans);
    }
}



Measured memory_bytes: 104592