fy:array[1..4] of longint=(0,1,0,-1);

var i,j,n,m,max,h:longint;

a:array[1..50,1..50] of char;

visit:array[0..50,0..50] of longint;

sum:array[1..2500] of longint;

procedure ini;

begin

readln(n,m);

for i:=1 to n do begin

for j:=1 to m do read(a[i,j]); readln;

end;

h:=0;

end;

procedure floodfill(i,j:longint);

var k,x,y:longint;

begin

for k:=1 to 4 do begin

x:=i+fx[k]; y:=j+fy[k];

if (x>0) and (x<n+1) and (y>0) and (y<m+1)

then begin

if visit[x,y]=1 then continue;

if a[x,y]='#' then continue;

visit[x,y]:=1; if a[x,y]='R' then inc(sum[h]);

a[x,y]:=chr(h+48);

floodfill(x,y);

end;

end;

end;

//main

begin

ini;

for i:=1 to n do

for j:=1 to m do if (a[i,j]='.') or (a[i,j]='R') then begin

inc(h);

if a[i,j]='R' then sum[h]:=1;

visit[i,j]:=1; a[i,j]:=chr(h+48);

floodfill(i,j);

end;

max:=0;

for i:=1 to h do if sum[h]>max then max:=sum[h];

writeln(max);

end.