#include <bits/stdc++.h>
#define MISAKA main
#define ll long long
using namespace std;
inline int read(){
	char ch=getchar();int f=1,x=0;
	while(ch<'0'||ch>'9'){if(ch=='-') f=-1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=(x<<3)+(x<<1)+(ch^48);ch=getchar();}
	return x*f;
}
const int N=6e3+10;
struct edge{int to,next;}e[N*N];
int head[N],deg[N],ecnt=-1,ans=0;
void add_edge(int u,int v){
	e[++ecnt].to=v;
	e[ecnt].next=head[u];
	head[u]=ecnt;
}
int vis[N],p[N],v[N],top=0,flag=0;
void dfs(int u,int f){
	p[++top]=u;vis[u]=1;
	for(int j=head[u];~j;j=e[j].next){
		if(e[j].to==f) continue;
		if(vis[e[j].to]) flag=1;
		else dfs(e[j].to,u);
	}
}
char mp[N>>1][N>>1];int n,m,K,B;
signed MISAKA(){
	//freopen("text.in","r",stdin); 
	memset(head,-1,sizeof(head));
	n=read(),m=read(),K=read(),B=read();
	for(int i=1;i<=n;i++) scanf("%s",(mp[i]+1));
	for(int i=1;i<=n;i++)	
		for(int j=1;j<=m;j++){
			if(mp[i][j]=='b'){
				add_edge(i,j+n);
				add_edge(j+n,i);
				deg[i]++,deg[j+n]++;
			}
		}
	for(int i=1;i<=n+m;i++){
		if(vis[i] || deg[i]==0) continue;
		top=0;flag=0;dfs(i,0);int sum=0;
		for(int j=1;j<=top;j++){
			v[p[j]]=1;
			if(p[j]<=n) for(int k=1;k<=m;k++) sum+=(!v[n+k])&&(mp[p[j]][k]=='k');
			else for(int k=1;k<=n;k++) sum+=(!v[k])&&(mp[k][p[j]-n]=='k');
		}
		if(flag) ans=max(ans,sum);
		else{
			for(int j=1;j<=top;j++){
				if(deg[p[j]]!=1) continue;
				int d=0;
				if(p[j]<=n) for(int k=1;k<=m;k++) d+=(!v[n+k])&&(mp[p[j]][k]=='k');
				else for(int k=1;k<=n;k++) d+=(!v[k])&&(mp[k][p[j]-n]=='k');
				ans=max(ans,sum-d);
			}
		}
		for(int j=1;j<=top;j++) v[p[j]]=0;
	}
	cout<<ans;
	return 0;
}