/*＿＿＿＿＿＿
　　 ||　　　　  　|
　　 ||ACはこちらへ|
　　 ||　　　　  　|
　　 ||￣￣￣￣￣￣ 
∧_∧||
(`･ω･||
（ つ||０
　uｰu*/
#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(ll i = 0; i < n; ++i)
using ll = long long ;
const ll INF = (1ll << 29);
const ll inf = INF*INF;
#define rall(x) (x).rbegin(),(x).rend()

int main(){
	ll n,m,c,x;
    cin >> n >> m >> c >> x;
    vector<vector<ll>> a(n,vector<ll>(m));
	rep(i,n) rep(j,m) cin >> a[i][j];

	auto sol = [&](ll mi){
		bool flag = false;
		vector<vector<ll>> dp(m,vector<ll>(2,-inf));
		rep(st,m) if(a[0][st]>=mi) dp[st][0] = 0;
		rep(i,n-1){
			vector<ll> best(2,-inf);
			ll id = -1;
			vector<vector<ll>> nextdp(m,vector<ll>(2,-inf));
			rep(j,m){
				ll ma = max(dp[j][0],dp[j][1]);
				if(best[0] < ma){
					best[1] = best[0];
					best[0] = ma;
					id = j;
				}else if(best[1] < ma){
					best[1] = ma;
				}}
			rep(j,m) {
				// f = 0
				if(a[i+1][j] >= mi) nextdp[j][0] = max(nextdp[j][0],best[(j == id?1:0)]);
				// f = 1
				if(min(a[i+1][j],a[i][j])>=mi+c) rep(t,2){
					nextdp[j][1] = max(nextdp[j][1],dp[j][t]+2-t);
				}
			}
			swap(nextdp,dp);
		}
		rep(i,m)rep(t,2) flag |= (dp[i][t]>=x); 
		return flag;
	};

	auto tansaku = [&](){
    	ll ok = -c,ng = 1e9+1;
    	while(abs(ok-ng) > 1){
        	ll mid = (ok + ng)/2;
        	if(sol(mid)) ok = mid;
        	else ng = mid;
	  	}
		return ok;
	};

	cout << tansaku() << endl;
}