#include<bits/stdc++.h>
#define FILE "read"
#define cmin(a,b) a=min(a,b)
#define cmax(a,b) a=max(a,b)
using namespace std;
int n,m,ans,cnt,vst[110],sum[110],check[110],f[110][110][110];
char ch[110][20];
inline int read(){
	int x=0,f=1;  char ch=getchar();
	while(!isdigit(ch))  {if(ch=='-')  f=-1;  ch=getchar();}
	while(isdigit(ch))  {x=x*10+ch-'0';  ch=getchar();}
	return x*f;
}
int get(int x){int temp(0);while(x)temp+=(x&1),x>>=1;return temp;}
bool judge(int x){return (!(x&(x<<1)))&&(!(x&(x<<2)));}
int main(){
	freopen(FILE".in","r",stdin);
	freopen(FILE".out","w",stdout);
	n=read();  m=read(); memset(f,-1,sizeof(f));
	for(int i=1;i<=n;++i) scanf("%s",ch[i]+1);
	for(int i=1;i<=n;++i) for(int j=1;j<=m;++j)
		if(ch[i][j]=='H') check[i]|=(1<<(j-1));
	for(int i=0;i<(1<<m);++i)if(judge(i))vst[++cnt]=i,sum[cnt]=get(i);
	for(int i=1;i<=cnt;++i)if(!(check[1]&vst[i]))f[1][i][1]=sum[i];
	for(int i=1;i<=n;++i)for(int j=1;j<=cnt;++j)if(!(check[i]&vst[j])){
		for(int k=1;k<=cnt;++k)if(!(vst[j]&vst[k])){
			for(int l=1;l<=cnt;++l)if(!(vst[j]&vst[l])){
				if(f[i-1][k][l]!=-1) cmax(f[i][j][k],f[i-1][k][l]+sum[j]);
			}
		}
	}
	for(int i=1;i<=cnt;++i)for(int j=1;j<=cnt;++j)cmax(ans,f[n][i][j]);
	printf("%d\n",ans);
}