#include <bits/stdc++.h>
#define pb push_back

using namespace std;
using ll = long long;

char s[255][255];

int a[255], b[255];
ll n, m, c, d;
int M, N;
int Map[255][255];
int p[255];
int vis[255];
void print() {
	for(int i = 1; i <= n; i++) {
		for(int j = 1; j <= m; j++) {
			cout << Map[i][j] << ' ';
		}
		cout << '\n';
	}
}
bool match(int i) {
	for(int j = 1; j <= N; j++) {
		if(Map[i][j] && !vis[j]) {
			vis[j] = 1;
			if(p[j] == 0 || match(p[j])) {
				p[j] = i;
				return true;
			}
		}
	}
	return 0;
}
ll ans = 0;
void fk() {
	int cnt = 0;
	ll tmp = ans;
	for(int i = 1; i <= M; i++) {
		memset(p, 0, sizeof(p));
		for (int j = 1; j <= M; j++) {
			memset(vis, 0, sizeof(vis));
			match(j);
		}
		int ok = 0;
		//		for(int j = 1; j <= M; j++) cout << p[j] << ' ';cout << '\n';
		for(int j = 1; j <= N; j++) {
			if(p[j]) {
				Map[p[j]][j] = 0;
				ok = 1;
				p[j] = 0;
				tmp -= d;
			}
		}
		if(ok) {
			tmp += c;
			ans = min(ans, tmp);
		}
	}
}
int main() {
	cin.tie(0) -> sync_with_stdio(0);
	cin >> n >> m >> c >> d;
	N = m, M = n;
	for(int i = 1; i <= n; i++) cin >> s[i] + 1;
	for(int i = 1; i <= n; i++) {
		for(int j = 1; j <= m; j++) {
			if(s[i][j] == '.') {
				ans += d;
				a[i]++, b[j]++;
				Map[i][j] = 1;
			}
		}
	}
	ll k = max(*max_element(a + 1, a + 251), *max_element(b + 1, b + 251));
	if (k == 0) {
		cout << "0\n";
		return 0;
	}
	fk();
	cout << ans << '\n';
	return 0;
}