program liukeke;
var
now:array[0..101] of longint;
a,b:array[0..102] of longint;
f:array[0..100,0..102,0..102] of longint;
n,m,i,k1,k2,k3,ans,j,tt,sum:longint;
s:string;
flag:boolean;

function max(a,b:longint):longint;
begin
if a>b then exit(a);
exit(b);
end;

procedure init;
var
i,j:longint;
ch:char;
begin
readln(n,m);
for i:=1 to n do
begin
for j:=1 to m do
begin
read(ch);
if ch='H' then
now[i]:=now[i] + (1<<(m-j));
end;
readln;
end;
end;

function change(x:longint):string;
begin
change:='';
while x>0 do
begin
change:=chr(x mod 2+48)+change;
x:=x div 2;
end;
end;

begin
assign(input,'connon.in');
reset(input);
assign(output,'connon.out');
rewrite(output);
init;
for i:=0 to (1<<m)-1 do
begin
tt:=0;
flag:=false;
s:=change(i);
while length(s)<m do s:='0'+s;
for j:=1 to m do
if s[j]='1' then
begin
if s[j+1]='1' then begin flag:=true; break; end;
if s[j+2]='1' then begin flag:=true; break; end;
inc(tt);
end;
if not flag then
begin
inc(sum);
a[sum]:=i;
b[sum]:=tt;
end;
end;
for i:=1 to sum do
f[1,i,1]:=b[i];
for i:=2 to n do
for k1:=1 to sum do
for k2:=1 to sum do
if (a[k1] and a[k2]=0)and(a[k1] and now[i]=0)and(a[k2] and now[i-1]=0)then
for k3:=1 to sum do
if (a[k1] and a[k3]=0)and(a[k2] and a[k3]=0)and(a[k3] and now[i-2]=0)then
f[i,k1,k2]:=max(f[i,k1,k2],f[i-1,k2,k3]+b[k1]);
for i:=1 to sum do
for j:=1 to sum do
if (a[i]and a[j]=0)and(a[i] and now[n]=0)and(a[j] and now[n-1]=0)then
ans:=max(ans,f[n,i,j]);
writeln(ans);
close(input);
close(output);
end.