program Project2;

uses
  SysUtils;

var n,m,i,j,m1,k,rec1:longint;
a:array[1..2,1..20,1..100000]of boolean;
ch:char;
t,b:boolean;


procedure rec(j:longint);
var m1,i,j1:longint;
begin
m1:=m;
t:=true;
j1:=j;
while t do
begin

t:=true;
for i:=1 to n do
begin
if a[1,i,m1]<>a[2,i,j1]then begin t:=false; break; end;
end;
  if t then begin dec(m1); end else rec(j+1);
if m1=0 then begin if b then begin rec1:=m-j; b:=false end; break; end;
if j1=1 then j1:=m else dec(j1);
end;

end;

begin
b:=true;
  assign(input,'repair.in');
reset(input);
assign(output,'repair.out');
rewrite(output);
readln(n,m);
for k:=1 to 2 do
for i:=1 to n do
begin
for j:=1 to m do
begin
read(ch);
if ch='.' then a[k,i,j]:=true;
end;
readln;
end;
close(input);

rec(1);
writeln(rec1);
close(output);
end.