program z5;

{$APPTYPE CONSOLE}

var f1,f2:text;
    a,b,n,i,j,l,b2,k,m:longint;
    ma:array [1..2,1..5] of byte;
    ss:byte;
    c:char;
    flag:boolean;
    sum:int64;

begin
assign(f1,'repair.in');
assign(f2,'repair.out');
reset(f1);
readln(f1,n,m);
k:=0;
for i:=1 to n*2 do
 begin
 for j:=1 to m do
  begin
   read(f1,c);
   if c='.' then ma[i,j]:=0 else ma[i,j]:=1;
  end;
  readln(f1);
 end;
close(f1);
rewrite(f2);
k:=0;
flag:=true;
for i:=1 to n do
   for j:=1 to m do
   if ma[i,j]<>ma[i+n,j] then flag:=false;

while flag=false do
 begin
  k:=k+1;
  for i:=1 to n do
   begin
    ss:=ma[i+n,m];
    for j:=m downto  2 do ma[i+n,j]:=ma[i+n,j-1];
    ma[i+n,1]:=ss;
   end;
  flag:=true;
  for i:=1 to n do
   for j:=1 to m do
   if ma[i,j]<>ma[i+n,j] then flag:=false;
 end;
writeln(f2,k);
close(f2);
end.