// 続けて同じものだとペナだと思ってたがそうは書いてない

use std::io::Write;
use std::collections::*;

type Map<K, V> = BTreeMap<K, V>;
type Set<T> = BTreeSet<T>;
type Deque<T> = VecDeque<T>;

fn main() {
    input! {
        n: usize,
        m: usize,
        c: i32,
        x: i32,
        a: [[i32; m]; n],
    }
    let mut deq = FoldableDeque::new(|a, b| std::cmp::max(*a, *b));
    let mut calc = |d: i32| -> bool {
        let inf = 10000;
        let mut dp = vec![[-inf, -inf]; m];
        for i in 0..m {
            if a[0][i] >= d {
                dp[i][0] = 0;
            }
        }
        for a in a.windows(2) {
            deq.clear();
            for dp in dp.iter() {
                deq.push_back(dp[0].max(dp[1]));
            }
                //println!("{:?} {:?}", deq.front, deq.back);
            for (i, dp) in dp.iter_mut().enumerate() {
                deq.pop_front();
                //println!("{:?} {:?}", deq.front, deq.back);
                let pre = *dp;
                dp[0] = -inf;
                if a[1][i] >= d {
                    dp[0] = deq.find().unwrap();
                }
                dp[1] = -inf;
                if a[0][i] - c >= d && a[1][i] - c >= d {
                    dp[1] = (pre[0] + 2).max(pre[1] + 1);
                }
                deq.push_back(pre[0].max(pre[1]));
            }
        }
        dp.iter().flatten().any(|dp| *dp >= x)
    };
    let mut ok = -10i32.pow(9);
    let mut ng = 10i32.pow(9) + 1;
    while ng - ok > 1 {
        let mid = ok + (ng - ok) / 2;
        if calc(mid) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    println!("{}", ok);
}

// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------
// ---------- begin Foldable Deque ----------
#[derive(Debug)]
pub struct FoldableDeque<T, F> {
    front: Vec<(T, T)>,
    back: Vec<(T, T)>,
    op: F,
}

impl<T, F> FoldableDeque<T, F>
where
    T: Clone,
    F: Fn(&T, &T) -> T,
{
    pub fn new(op: F) -> Self {
        FoldableDeque {
            front: Vec::new(),
            back: Vec::new(),
            op: op,
        }
    }
    pub fn find(&self) -> Option<T> {
        match (self.front.last(), self.back.last()) {
            (Some(a), Some(b)) => Some((self.op)(&a.1, &b.1)),
            (x, y) => x.or(y).map(|p| p.1.clone()),
        }
    }
    pub fn clear(&mut self) {
        self.front.clear();
        self.back.clear();
    }
    pub fn len(&self) -> usize {
        self.front.len() + self.back.len()
    }
    pub fn push_back(&mut self, val: T) {
        let sum = match self.back.last() {
            Some(p) => (self.op)(&p.1, &val),
            None => val.clone(),
        };
        self.back.push((val, sum));
    }
    pub fn push_front(&mut self, val: T) {
        let sum = match self.front.last() {
            Some(p) => (self.op)(&val, &p.1),
            None => val.clone(),
        };
        self.front.push((val, sum));
    }
    pub fn pop_front(&mut self) -> Option<T> {
        if self.front.is_empty() {
            let mut back = std::mem::take(&mut self.back);
            let m = (back.len() + 1) / 2;
            for (v, _) in back.drain(..m).rev() {
                self.push_front(v);
            }
            if !back.is_empty() {
                back[0].1 = back[0].0.clone();
                let (f, t) = back.split_at_mut(1);
                let mut pre = &f[0].1;
                for b in t.iter_mut() {
                    b.1 = (self.op)(pre, &b.0);
                    pre = &b.1;
                }
            }
            self.back = back;
        }
        self.front.pop().map(|p| p.0)
    }
    pub fn pop_back(&mut self) -> Option<T> {
        if self.back.is_empty() {
            let mut front = std::mem::take(&mut self.front);
            let m = (front.len() + 1) / 2;
            for (v, _) in front.drain(..m).rev() {
                self.push_back(v);
            }
            if !front.is_empty() {
                front[0].1 = front[0].0.clone();
                let (t, f) = front.split_at_mut(1);
                let mut pre = &t[0].1;
                for f in f.iter_mut() {
                    f.1 = (self.op)(&f.0, pre);
                    pre = &f.1;
                }
            }
            self.front = front;
        }
        self.back.pop().map(|p| p.0)
    }
    pub fn front(&self) -> Option<&T> {
        self.front.last().or_else(|| self.back.get(0)).map(|p| &p.0)
    }
    pub fn back(&self) -> Option<&T> {
        self.back.last().or_else(|| self.front.get(0)).map(|p| &p.0)
    }
    pub fn get(&self, k: usize) -> Option<&T> {
        let f = self.front.len();
        self.front
            .get(f - 1 - k)
            .or_else(|| self.back.get(k - f))
            .map(|p| &p.0)
    }
}
// ---------- end Foldable Deque ----------