#include<bits/stdc++.h>
using namespace std;
int main(){
	int h,w,f;
	char c;
	cin>>h>>w>>c>>f;
	string s1(w,c),s2(w,' ');
	if(f==0) s2[0]=s2[w-1]=c;
	else s2=s1;
	for(int i=1;i<=h;i++){
		if(i==1||i==h) cout<<s1<<endl;
		else cout<<s2<<endl;
	}
	return 0;
}