{
TASK:rprimes
LANG:PASCAL
}
program rprimes;
var
  a,b,ans:longint;
function is_prime(num:longint):boolean;
var
  i:longint;
begin
 if num=1 then begin is_prime:=false; exit; end;
 if num=2 then begin is_prime:=true; exit; end;
 for i:=2 to trunc(sqrt(num)) do
  if num mod i=0 then
  begin
   is_prime:=false;
   exit;
  end;
 is_prime:=true;
end;
procedure gen(num:longint);
begin
 if (num>=a) and (num<=b) then ans:=ans+1;
 if (is_prime(num*10+1)) and (num*10+1<=b) then gen(num*10+1);
 if (is_prime(num*10+3)) and (num*10+3<=b) then gen(num*10+3);
 if (is_prime(num*10+7)) and (num*10+7<=b) then gen(num*10+7);
 if (is_prime(num*10+9)) and (num*10+9<=b) then gen(num*10+9);
end;
begin
   readln(a,b);
   ans:=0;
   gen(2);
   gen(3);
   gen(5);
   gen(7);
   writeln(ans);
   readln
end.