/*＿＿＿＿＿＿
　　 ||　　　　  　|
　　 ||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 all(x) (x).begin(),(x).end()
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 up2 = [&](vector<pair<ll,ll>> &vp,ll d,ll id){
		vp.push_back(make_pair(d,id));
		sort(all(vp));
		if(vp.size()>=2) vp.pop_back();
		return;
	};
	auto chmin = [&](ll &a, ll b){
		a = min(a,b);
		return;
	};
	auto sol = [&](ll mi){
		bool flag = false;
		rep(st,m){
			vector<vector<ll>> dp(n+1,vector<ll>(m,x+1));
			dp[0][st] = 0;
			rep(i,n-1){
				vector<pair<ll,ll>> vp;
				rep(j,m) if(dp[i][j]<= x) up2(vp,dp[i][j],j);
				rep(j,m)for(auto k:vp){
					if(j == k.second && min(a[i+1][j],a[i][j])>=mi+c) chmin(dp[i+1][j],dp[i][j]+1);
					else if(j != k.second && a[i+1][j]>=mi && a[i][k.second]>= mi) chmin(dp[i+1][j],dp[i][k.second]);
				}
			}
			if(min(a[0][st],a[n-1][st])<mi+c) dp[n-1][st] = x+1;
			else ++dp[n-1][st];
			rep(i,m) flag |= (dp[n-1][i]<=x); 
		}
		return flag;
	};
	auto tansaku = [&](){
    	ll ok = -1,ng = inf;
    	while(abs(ok-ng) > 1){
        	ll mid = (ok + ng)/2;
			// ll mid = l + (r-l)/2;
        	if(sol(mid)) ok = mid;
        	else ng = mid;
	  	}
		return ok;
	};
	cout << tansaku() << endl;
}