#include<bits/stdc++.h>
#define re register
using namespace std;
inline int read(){
	re int t=0;re char v=getchar();
	while(v<'0')v=getchar();
	while(v>='0')t=(t<<3)+(t<<1)+v-48,v=getchar();
	return t;
}
const int M=998244353;
inline void add(re int &x,re int y){(x+=y)>=M?x-=M:x;}
inline int Mod(re int x){return x>=M?x-M:x;}
inline int ksm(re int x,re int y){
	re int s=1;
	while(y){
		if(y&1)s=1ll*s*x%M;
		x=1ll*x*x%M,y>>=1;
	}
	return s;
}
int n,m,fa[6002],ih[6002],val[6002],ans,deg[6002];
char s[3002][3002];
inline int root(re int x){return x==fa[x]?x:fa[x]=root(fa[x]);}
inline void Merge(re int x,re int y){
	++deg[x],++deg[y],x=root(x),y=root(y);
	if(x==y){ih[x]=1;return;}
	fa[x]=y,ih[y]|=ih[x];
}
int main(){
	n=read(),m=read(),read(),read();
	for(re int i=1;i<=n;++i)scanf("%s",s[i]+1);
	for(re int i=1;i<=n+m;++i)fa[i]=i;
	for(re int i=1;i<=n;++i)
		for(re int j=1;j<=m;++j)
			if(s[i][j]=='b')
				Merge(i,j+n);
	for(re int i=1;i<=n;++i)
		for(re int j=1;j<=m;++j)
			if(s[i][j]=='k'){
				++val[root(i)];
				if(root(j+n)!=root(i))++val[root(j+n)];
			}
	for(re int i=1;i<=n+m;++i)if(ih[i])ans=max(ans,val[i]);
	for(re int i=1;i<=n;++i)
		if(deg[i]==1){
			re int vv=val[root(i)];
			for(re int j=1;j<=m;++j)if(s[i][j]=='k'&&root(j+n)!=root(i))--vv;
			ans=max(ans,vv); 
		}
	for(re int j=1;j<=m;++j)
		if(deg[j+n]==1){
			re int vv=val[root(j+n)];
			for(re int i=1;i<=n;++i)if(s[i][j]=='k'&&root(j+n)!=root(i))--vv;
			ans=max(ans,vv);
		}
	printf("%d",ans);
}