fm.cpp

#include <iostream>
#include <stdio.h>
 
using namespace std;
 
 
bool coversRegion(int startR,int startC,int Ar,int Ac,int Tr,int Tc,char grid[1000][1000]){
	for(int i = 0;i<Tr;i++){
		if(startR+i<0)continue;
		if(startR+i>=Ar)break;
		for(int j=0;j<Tc;j++){
			if(startC+j<0)continue;
			if(startC+j>=Ac)break;
			if(grid[startR+i][startC+j]=='X') return true;
		}
	}
	return false;
}
 
int countTiles(int startR,int startC,int Ar,int Ac,int Tr,int Tc,char grid[1000][1000]){
	int count = 0;
	for(int i=startR;i<Ar;i+=Tr){
		for(int j=startC;j<Ac;j+=Tc){
			if(coversRegion(i,j,Ar,Ac,Tr,Tc,grid))count++;
		}
	}
	return count;
}
 
int countMinimum(int Ar,int Ac,int Tr,int Tc,char grid[1000][1000]){
	int minTiles = 1000000;
	for(int i = 1-Tr;i <= 0;i++){
		for(int j=1-Tc;j<=0;j++){
			int temp = countTiles(i,j,Ar,Ac,Tr,Tc,grid);
			if(temp < minTiles) minTiles = temp;
		}
	} 
	return minTiles;
}
 
int main(){
	int Ar,Ac,Tr,Tc;
	char grid[1000][1000];
	while(cin >> Ar >> Ac >> Tr >> Tc){
		for(int i=0;i<Ar;i++){
			char a;
			scanf("%c",&a);
			for(int j=0;j<Ac;j++){
				scanf("%c",&grid[i][j]);
			}
		}
		cout << countMinimum(Ar,Ac,Tr,Tc,grid) << endl;
	}
	return 0;
}