fm.cpp

#include <cstdio>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits.h>
#include <map>
#include <queue>
#include <vector>
#include <set>
#include <stack>
#include <bitset>
#include <string>
 
using namespace std;
 
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef set<int> si;
typedef set<ii> sii;
 
#define MP make_pair
#define PB push_back
#define REP(i,a) for ( int i = 0; i < int(a); i++)
#define FOR(i,a,b) for ( int i = int(a); i<=int(b); i++)
#define FORD(i,a,b) for(int i= int(a); i>=int(b); i--)
 
const int INF = 1<<29;
typedef long long int ll;
 
int  ar, ac, tr, tc;
char board[1001][1001];
 
bool isIn( int r1, int r2, int c1, int c2 )
{
	r1 = max( r1, 0 );
	r2 = min( r2, ar - 1 );
	c1 = max( c1, 0 );
	c2 = min( c2, ac - 1 );
	//printf("%d %d %d %d\n", r1, r2, c1, c2);
	FOR( i, r1, r2 )
		FOR( j, c1, c2 ) 
			if ( board[i][j] == 'X' )
				return true;
	return false;
}
 
int countTiles( int r, int c )
{
	int count = 0;
	for ( int i = r; i < ar; i += tr )
		for ( int j = c; j < ac; j += tc )
			if ( isIn( i, i+tr-1, j, j+tc-1 ) ) {
				++count;
        //printf("YEP\n");
      }
	return count;
}
 
int main()
{
	while ( scanf("%d%d%d%d", &ar, &ac, &tr, &tc) == 4 )
	{
		FOR( i, 0, ar-1 )
		{
			FOR( j, 0, ac-1 )
				scanf(" %c", &board[i][j]);
			//scanf("%*c");
		}
		int count = INT_MAX;
		FOR( i, -tr+1, 0 )
			FOR( j, -tc+1, 0 )
			{
				int tmp = countTiles( i, j );
        count = min( count, tmp );
				//printf("%d-%d\n", tmp, count);
			}
		printf("%d\n", count);
	//	break;
	}
	return 0;
}