use std::cmp::*; // https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_rules! input { ($($r:tt)*) => { let stdin = std::io::stdin(); let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); let mut next = move || -> String{ bytes.by_ref().map(|r|r.unwrap() as char) .skip_while(|c|c.is_whitespace()) .take_while(|c|!c.is_whitespace()) .collect() }; input_inner!{next, $($r)*} }; } macro_rules! input_inner { ($next:expr) => {}; ($next:expr,) => {}; ($next:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($r)*} }; } macro_rules! read_value { ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } fn main() { input! { n: usize, m: usize, a: [i64; n], b: [i64; m], } const INF: i64 = 1 << 50; let mut pos = 0; let mut ans = INF; for i in 0..n + 1 { let lo = if i == 0 { -INF } else { a[i - 1] }; let hi = if i == n { INF } else { a[i] }; let mut dp = vec![lo]; while pos < n && b[pos] < hi { dp.push(b[pos]); pos += 1; } dp.push(hi); let mut ma = 0; for i in 0..dp.len() - 1 { ma = max(ma, dp[i + 1] - dp[i]); } ans = min(ans, hi - lo - ma); } println!("{}", ans); }