/*
@Date    : 2024-05-23 15:59:04
@Author  : Adscn ([email protected])
@Link    : http://www.cnblogs.com/LLCSBlog
*/
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define IL inline
#define RG register
#define gi geti<int>()
#define gl geti<ll>()
#define gc getchar()
#define File(a) freopen(a".in","r",stdin);freopen(a".out","w",stdout)
template<typename T>IL bool chkmax(T &x,const T &y){return x<y?x=y,1:0;}
template<typename T>IL bool chkmin(T &x,const T &y){return x>y?x=y,1:0;}
template<typename T>
IL T geti()
{
	RG T xi=0;
	RG char ch=gc;
	bool f=0;
	while(!isdigit(ch))ch=='-'?f=1:f,ch=gc;
	while(isdigit(ch))xi=xi*10+ch-48,ch=gc;
	return f?-xi:xi;
}
template<typename T>
IL void pi(T k,char ch=0)
{
	if(k<0)k=-k,putchar('-');
	if(k>=10)pi(k/10);
	putchar(k%10+'0');
	if(ch)putchar(ch);
}
/*
IL unsigned int LOG2(unsigned int x)
{
	unsigned int ret;
	__asm__ __volatile__ ("bsrl %1, %%eax":"=a"(ret):"m"(x));
	return ret;
}
*/
const int N=251;
const int V=N*N*2+3*N;
const int E=N*N*4;
struct edge{
	int v,nxt,w;
}e[E<<1];
int head[V],cnt;
void init(){
	memset(head,cnt=-1,sizeof head);
}
void add(int u,int v,int w){
	e[++cnt]=(edge){v,head[u],w};
	head[u]=cnt;
}
void link(int u,int v,int w){
	add(u,v,w);
	add(v,u,0);
}
int dis[V];
int cur[V];
int S,T;
bool bfs(){
	queue<int>q;
	memset(dis,0,sizeof dis);
	q.push(S);
	memcpy(cur,head,sizeof head);
	dis[S]=1;
	while(!q.empty())
	{
		int u=q.front();q.pop();
		for(int i=head[u];~i;i=e[i].nxt){
			int v=e[i].v;
			if(!dis[v]&&e[i].w!=0){
//				printf("(%d,%d,%d)\n",u,v,e[i].w);
				dis[v]=dis[u]+1;
				if(v==T)return 1;
				q.push(v);
			}
		}
	}
	return 0;
}
int dfs(int maxflow,int x){
//	printf("maxflow=%d x=%d\n",maxflow,x);
	if(!maxflow||x==T)return maxflow;
	int resflow=maxflow;
	for(int &i=cur[x];~i;i=e[i].nxt){
		int v=e[i].v,flow=0;
		assert(x!=v);
		if(e[i].w&&dis[v]==dis[x]+1&&(flow=dfs(min(resflow,e[i].w),v))){
			resflow-=flow;
			e[i].w-=flow;
			e[i^1].w+=flow;
			if(!resflow)break;
		}
	}
	return maxflow-resflow;
}
char c[N][N];
int n,m,maxk;
int id_row(int id){
	return id;
}
int id_col(int id){
	return id+n;
}
int id_point(int x,int y){
	return n+m+(x-1)*m+y;
}
int main(void)
{
	#ifndef ONLINE_JUDGE
//	File("");
	#endif
	init();
	n=gi,m=gi;
	ll C=gi,d=gi;
	int cnt=0;
	for(int i=1;i<=n;++i){
		scanf("%s",c[i]+1);
		for(int j=1;j<=m;++j)
			if(c[i][j]=='.')
				cnt++;
	}
	maxk=max(n,m);
	S=0,T=maxk*maxk*2+n+m+1;
	ll ans=d*cnt;
	ll flow=0;
	for(int i=1;i<=n;++i){
		link(S,id_row(i),1);
	}
	for(int i=1;i<=m;++i){
		link(id_col(i),T,1);
	}
	for(int i=1;i<=m;++i)
		for(int j=1;j<=n;++j)
			if(c[j][i]=='.')
				link(id_row(j),id_point(j,i),1);
	for(int i=1;i<=n;++i)
		for(int j=1;j<=m;++j)
			if(c[i][j]=='.')
				link(id_point(i,j),id_col(j),1);
	for(int k=1;k<=maxk;++k){
		while(bfs()){
			int res=dfs(1e9,S);
//			printf("Res=%d\n",res);
//			printf("\n\n");
			flow+=res;
		}
//		printf("k=%d flow=%d\n",k,flow);
		chkmin(ans,k*C+d*(cnt-flow));
		for(int i=0;i<n+m;++i)e[i*2].w++;
	}
	pi(ans);
	return 0;
}