{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  y1,y2 : array [0..100000] of integer;
  sols : array [1..100000] of integer;
  s1,s2 : string;
  i,l,p,f1,f2 : integer;

function comp(x : integer) : boolean;
var i : integer;
a : boolean;
begin
a := true;
for i := 1 to x do
  if s1[i] <> s2[l-x+i] then
    begin
      a := false;
      exit;
    end;
comp := a;
end;

begin
  assign(input,'k.in');
  assign(output,'k.out');
  reset(input);
  rewrite(output);
  readln(s1);
  readln(s2);
  l := length(s1);
  p := 1;
  f1 := 0;
  f2 := 0;
  for i := 1 to l do
    begin
      if s1[i] = '1' then inc(f1);
      if s2[l-i+1] = '1' then inc(f2);
      if f1 = f2 then
        begin
          sols[p] := i;
          inc(p);
        end;
    end;
  dec(p);
  while (p > 0) and not comp(sols[p]) do dec(p);
  if p = 0 then writeln(l) else writeln(l-sols[p]);
end.