var a,b,s,m,n :integer;  f,g:text;
begin
assign(f,'cmmdc.in'); reset(f);
 readln(f,a,b);
 close(f);
 for n:=1 to a do
begin
if a mod 2=1 then
n:=a+1
end;
for n:=1 to a do
begin
if b mod 2=1 then
 m:=b+1
end;
 if m=n then s:=n;
 if m<>n then s:=0;
assign(g,'adunare.out'); rewrite(g);
writeln(g,s);
close(g);
end.