program mire;
var m,p,min,c,d:int64;
a,b,n,i:longint;
function cmmdc(x,y:longint):longint;
var r,aux:longint;
begin
   if x<y then
     begin
       aux:=x;
       x:=y;
       y:=aux;
     end;
   repeat
     r:=x mod y;
     x:=y;
     y:=r;
   until y=0;
 cmmdc:=x;
end;
begin
   read(a,b);
 if (a=0) or (b=0) then
   write(0)
  else
 if (cmmdc(a,b)=1) or (a mod b=0) or (b mod a=0) then
   write(0)
  else
    begin
     min:=1000000000;
      for i:=1 to b do
         begin
           c:=a+i;
           d:=b+i;
           m:=cmmdc(c,d);
           p:=c div m *d;
           if p<min then
             begin
                min:=p;
                n:=i;
             end;
         end;
       write(n);
    end;
end.